Rick Escalambre

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Updated 01/26/2023.

Copyright© 2023 RL Escalambre. All rights reserved.   

About Rick Escalambre image
Rick Escalambre earned his bachelor's degree in Industrial Arts from San Francisco State University. He has been a part of the automotive industry for 49 years. He previously taught high school automotive courses, managed a Chevron Service Station, and owned and operated a general automotive repair business in Concord, CA.

He taught full-time at Skyline College in San Bruno, CA, for 31 years. As of June 2015, he retired from full-time teaching and continues to teach part-time and do contract training. In addition to teaching Engine Performance related subjects, he coordinated one of California's largest and finest automotive programs.

College’s facility, equipment, dynamometers, and vehicles allowed him to conduct in-depth research on Engine performance, Computer Controls, On-Board Diagnostic Two (OBDII) System Operation & Diagnosis, and Evaporative Emission Systems.

Rick is a respected author and editor of books on Engine Performance, Evaporative Emission Systems, and Computer Controls. He aims to provide information to help teachers and technicians perform their jobs more effectively.

The official start of On-Board Diagnostics I (OBD I) was in 1988 (1). At that time, the California Air Resources Board (CARB) required that all vehicles sold new in California be equipped with a Check Engine Light (CEL). CARB required manufacturers to monitor the items in the area (2) below.

On-Board Diagnostics II (OBD II) was officially required to be equipped on all 1996 and newer passenger cars and light-duty trucks. Some manufacturers installed OBD II on 1994 and 1995 model-year vehicles. CARB required manufacturers to monitor the below items in the area (5).
The basic principles of Computer Fundamentals do not change. The foundation is always Input, Process, and Output. An important note is to look at where the scan tool is placed in the system. It takes processed data from the PCM and decodes it so the technician can read it. Remember that connecting a scan tool means adding another module to the network.

I-P-O principles: Input, Process, and Output apply to every computer in use today. The sequence of Input, Process, and Output is vital to proper system operation. The basic principles of Computer Fundamentals do not change.

Computer Fundamentals I-P-O

One important note: look at where the scan tool is placed in the system. Sensors and Switches provide the Input to the Processor as raw, non-processed data; the PCM processes the data and issues digital commands to the Outputs. The scan tool decodes the processed data so the technician can read the information.


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An automotive scan tool is an electronic device the technician uses to decode serial data, communicate with modules, diagnose problems, and sometimes reprogram vehicle control modules.

Remember that a scan tool is only as good as the user’s understanding of the data. When used with the proper reference materials, a scan tool can significantly help a knowledgeable, experienced technician performing computer-related diagnostics. Often the device is more than a help; it's a necessity. But it cannot solve problems by itself. Understanding the data and accurately interpreting the information displayed is the key. The technician, not the tool, is the diagnostician.

Four Types of Scan Tools are available: 

  1. Code Readers – They are inexpensive and quick but do not provide all the Global MODEs.
  2. Bluetooth for Smartphones – moderately priced but does not provide all the Global MODEs.
  3. Aftermarket with complete Global OBD II and Enhanced (OEM Level). 
  4. OEM factory specific, but may not include any, or all, of Global OBD II MODEs.

A scan tool can be Wired or Wireless (Bluetooth), handheld or PC based. To achieve a higher level of diagnostics, an essential Code Reader or Bluetooth for IOS and Smartphones will not do the job.

Two options are available when using an aftermarket scan tool, technician and there are advantages to both:

Global (EOBD) OBD II: 

  1. Does not identify the system by Make, Model, or Year. 
  2. Talks in standard Protocols to all systems. • Pre-CAN PIDS can be limited. 
  3. CAN PIDS can be extensive and provide some PIDS the Enhanced Scan Tool does not provide. 
  4. Can provide many PIDS similar to Enhanced OBD II but may identify them using different terminology. 
  5. If available, provide minimal Bi-Directional Testing using the EVAP Vent Solenoid.

Enhanced (OEM) OBD II: 

  1. Does identify the system by VIN, Make, Model, and Year. 
  2. Talks using Protocol specifically used by that manufacturer. 
  3. Can provide many PIDS similar to Global but may identify them using different terminology. 
  4. Can provide PIDS not found in Global OBD II. PIDS may be divided into pages. 
  5. Provides Bi-Directional Testing of specific Outputs. 
  6. It may provide reprogramming options.

Many times, with pre-Can OBD II, technicians would choose the enhanced side of the scan tool. This was because it offered more PIDs.   

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MODE $01Readiness Flag Status and Parameter Identification (PIDs)


MODE $02Powertrain Freeze Frame Data (FFD)


MODE $03Emission Related Diagnostic Trouble Codes (DTC)


MODE $04Clear/Reset Emission Related Diagnostic Information


MODE $05
Oxygen Sensor Monitoring Test Results


MODE $06Onboard Monitoring Test Results and Parameters


MODE $07Two Trip Pending Diagnostic Trouble Code


MODE $08Request Control of Onboard Component


MODE $09Request Vehicle Information


MODE $0a
Permanent Diagnostic Trouble Code (PDTC)


Some aftermarket scan tools will display the Hexadecimal symbol ($), others will not.

Snap-On Global Scan Tool


AUTEL Global Scan Tool

MODE $01 Parameter Identification (PID) displays emission-related data PIDs such as inputs, outputs, and system status.  Pre-CAN global OBD II displayed between 15-30 PIDs.  For CAN systems the data list was expanded.  When using a global scan tool to diagnose the vehicle understand the amount of data available to view and that it will vary depending on the model year and communications protocol.

The following are three examples of what to expect for data PIDs.

1) This data list was captured from a 1997 pre-CAN vehicle. Because of the limited data displayed from some pre-CAN systems, many technicians chose to look at the manufacturer's (OE) specific data. In many but not all cases, this side of the scan tool displayed much more data.

2) This data list was captured from a 2003 pre-CAN vehicle. For later model pre-CAN systems, the data list provided enough data to diagnose many emissions-related problems, but the data list still needed to be expanded.

3) This data list was captured from a 2019 CAN-equipped vehicle. Because CAN systems transmit data at a much faster speed and in packets of 6 PIDs per request the data list was expanded. In this case, a technician had more help to diagnose more problems through the global side of the scan tool.

Regardless of the year vehicle, learn to customize the PID list to increase the speed at which they update their data. Focus on the need-to-know PIDs, not the nice-to-know PIDs. Think of it this way, you have a one-lane road and there are only 6 cars on the road moving at the same speed. The next time you drive that road there are 30 cars on the road moving at the same speed. Which one is faster to travel through?

MODE $01 includes the Readiness Flag Status.  Readiness flag status can show if testing of each flag completed testing a minimum of one time since the memory was the last reset. This information can be used to verify a repair by running specific monitor test(s) that will flip the readiness flag to COMPLETE. State Emission Testing programs also use it as one of the requirements to pass or fail an OBD inspection. 

This example shows the readiness flag status since the memory was last cleared. Once COMPLETE, it can only be changed back to Incomplete by performing a MODE $04 diagnostic clear or removing power from or reprogramming the Engine Control Module (ECM).

Suppose all readiness flags are COMPLtoer to verify a repair or to turn out a MalfuncIndicatoriator Lamp (MIL) without resetting the memory. In that case, there is an option to view the status of the current drive cycle. At each key-on, all readiness flags will display as Incomplete. As the monitor test required to flip a readiness flag to complete runs and passes, the status will be updated to COMPLETE. If any readiness flag remains INCOMPLETE, the monitor test required to flip the flag did not run and complete. Note: this open is only available while connected to a CAN-equipped system.


A Freeze Frame of High Priority will over right a stored FFD of lower priority.  Newer same priority DTC/FFD will not over right a previously stored FFD of the same priority.

There is only one FFD stored per system. Think of it as having one seat for two people or more people (remember musical chairs?

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A diagnostic trouble code (DTC) Indicates the enable criteria for a monitor test has failed outside of a minimum or maximum test limit. If the MIL is illuminated tailpipe emissions have exceeded 1.5 times the Federal Test Procedure (FTP) standards. This can occur on the first or second consecutive trip.

All DTCs represented by a five-digit alphanumeric code. The first letter indicates the function of the monitored component or system that has failed:
P = Powertrain
B = Body
C = Chassis
U = Indicates a network or data link code
The second digit is represented by a number that indicates who is responsible the code:
0 = Society of Automotive Engineers (SAE)
1 = Manufacturer specific

The third digit indicates the specific system in question. Numbers one through seven indicate a powertrain related problem. The number eight is reserved for non-powertrain related problems:
0 = Total system
1 = Air/Fuel metering control
2 = Air/Fuel metering control for injector circuit malfunctions only.
3 = Ignition system or misfire
4 = Emissions Control
5 = Vehicle speed Control and Idle Control system
6 = ECM and Computer Input/Output Circuits
7 = Transmission
8 = Non-Powertrain related
The fourth and fifth digits represents the component, system, or area experiencing the problem.
Using DTC P0306 shown in figure 12-17 is described as:
P = Powertrain related
O = Manufacturer defined DTC
3 = Ignition system or misfire related problem
06 = Cylinder #6 misfire detected.This MODE retrieves from the PCM all stored emission related DTCs.


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This MODE allows for the clearing and resetting of all DTCs (MODE $03), freeze frame data (MODE $02), readiness flag results (MODE $01), and test results values (MODEs $05 & $06).

When attempting to perform a Clearing of Diagnostic information, the Technician will always be asked: Do you wish to Continue?

The reason is that you may be clearing information that could help diagnose the problem. Or, clearing the Monitors could cause someone to fail a Smog Inspection.
MODE $04 does not clear learned or adaptive strategies.

MODE $05 displays test results for the most recent oxygen sensor monitor tests. They’re stored and are not live values. It did not support Air Fuel Ratio Sensors (AFRS).

This MODE is no longer supported for CAN "C" systems; related information will be found in MODE $06.

MODE $05 is the latest Monitor Tests results for the Oxygen Sensors. It is not “live” data. It is stored in memory and replaced with newer test results.
The problem with this MODE is that not all manufacturers supported MODE $05. Also, this MODE did not allow the addition of Air Fuel Sensors.

Under CAN Regulations, MODE $05 was eliminated and moved to MODE $06.

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MODE $06 Introduction

MODE $06 is one of 15 modes available to Global OBD II. It provides monitor test results for non-continuous monitors and sometimes continuous monitors. MODE $06 requests the ECM to view monitor test results reported after the test runs.

The ECM compares test results to the limits and reports a Pass or Fail result to the scan tool for each monitored system and component.  This MODE will report results in one trip if the monitor runs. They’re stored and are not live values.

How can it help diagnose vehicle emission-related concerns? MODE $06 monitor test results can help confirm the success of repairs for a non-continuous. MODE $06 test values (and pending DTCs) are available to the technician on a two-trip monitor’s first trip. MODE $06 test results can indicate if a monitored system (component) is close to failing a monitor test.

MODE $06 Terminology

Pre-CAN Systems: 

  • TID = Test Identification – The system (EVAP, CAT, O2, EGR, etc.) being tested. 
  • CID = Component Identification – The component or area of the system being tested.

The problem with pre-CAN MODE $06 was that TID/CID was not standardized. The following chart shows the TID/CID for a Toyota/Lexus. These numbers will be completely different when looking at other manufacturers.

CAN "C" Equipped Systems: 

  • MID = Monitor Identification: The non-continuous system (EVAP, CAT, O2, EGR, VVT, AIR) or continuous system (Misfire, Fuel system, etc.) being tested. 
  • TID = Test Identification – Specific monitor test being tested.

The chart shown below identifies MIDS for CAN "C" systems. Regardless of the manufacturer, these MIDS are standardized for all vehicles.  Some scan tools will report them by MID and not use the Monitor ID name. Some scan tools will report them using the MID and the Monitor name. Regardless, this chart applies to all CAN "C" vehicles. 

RELATED TERMINOLOGY: 

  • Test Limit Type: To pass a test, the value must be either a minimum or maximum value (or between a min/max value) 
  • Hexadecimal ($): Numeric/Alpha unit that indicates a specific TID/CID or test value (Example: $02) 
  • Raw Data: Test data shown in a decimal number indicating the actual test results. 
  • Manufacturer’s Conversion: A value supplied by the manufacturer to convert this data to values that can be used to diagnose a system (volts, Ohms, amps, inches of mercury, etc.). 
  • Test Value: = Actual test results. 
  • Test Result: = Indicates whether the system/component passed or failed a test.

MODE $06 Reporting Formats

Pre-CAN systems: Here is how the PCM and Scan Tool report the Test Results. 

Step 1: The PCM communicates in Hexadecimal, a combination of numbers and letters. 

Step 2:  The Scan Tool reports the results in Decimal format.  It does not show the test's name or the result's actual values.

Step 3:  The scan tool reports the monitor test name and unit value. Before CAN, this required using a manufacturer’s scan tool because unit conversion numbers differed. There was no way for an aftermarket scan tool manufacturer to keep up with the changes.

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For most OBD II strategies, the same malfunction must occur on two separate driving events to illuminate the MIL. This “double” detection ensures that a malfunction truly exists before alerting the owner. The first time a malfunction is detected, a “pending” fault code, which identifies the failing component or system, is stored in the onboard computer. If the same malfunction is again detected the next time the vehicle is operated, the MIL is illuminated and a “confirmed” fault code is stored. When the MIL is illuminated (alerting the vehicle operator to a problem) and a vehicle is brought in for service, a technician uses the “confirmed” fault code to determine what system or component has failed. A “pending” fault code, however, can be used by service technicians to help diagnose intermittent problems as well as to verify that repairs were successful. In these instances, a technician can use the “pending” fault code as a quicker, earlier warning of a suspected (but as yet unconfirmed) problem.

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This MODE enables the scan tool to request the PCM to command the EVAP Vent On.

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A Permanent Diagnostic Troubles Code (PDTC) can be set by any confirmed DTC currently commanding the MIL On. They first appeared in 2010 as part of a three-year phase-in period. By the 2012 model year, all vehicles could set a PDTC. The ECM must have enough memory to store a minimum of four permanent DTCs. 

The following capture is an example of the three possible DTCs:  a Pending DTC (MODE $07), a stored DTC (MODE $03), and a Permanent Diagnostic Trouble Code (MODE $0a).

A PDTC is designed to prevent a stored DTC (MODE $03) from being erased before going in for a state emissions test. This prevents a vehicle that would typically fail from passing. PDTCs are stored in non-volatile ram (NVRAM) to prevent them from being erased with the scan tool or by removing battery power to the ECM. 

A PDTC can only be erased from memory if the OBD system extinguishes the MIL (e.g., when the current DTC changes to a History DTC). If the memory is not cleared with a scan tool, the ECM will need to see the related monitor test complete and pass on three consecutive trips. The PDTC will not be removed from memory until the fourth key-on cycle. If the memory is cleared with the scan tool, the MIL will be extinguished; the MODE $03 DTC and MODE $02 Freeze Frame Data will be cleared. The PDTC will still be in memory, but it will take only one good trip to remove it from memory. 

If multiple PDTCs are present, it could take many trips and miles to clear them from memory. This should not affect driveability or emissions if the stored MODE $03 DTC is no longer present. Initially, there were many issues with clearing a Permanent Diagnostic Trouble Code. Eventually, these issues were resolved by reprogramming the ECM.

For a Misfire and Fuel System PDTC, the ECM must support storing up to four similar conditions window (SCW) in NVRAM to allow proper clearing from memory. If a Misfire of Fuel System PDTC is stored during the first occurrence, the ECM must store an SCW that includes: engine speed +/- 375 rpm, engine load +/-20 %, and the same warmup condition below 160°F or 160°F and above. The SCW allows the ECM to monitor the specific Misfire/Fuel system conditions when the DTC was initially set. If additional Misfire or Fuel System DTCs are set, each must store a SCW.

Chrysler is the only manufacturer to provide this information through their factory scan tool. This is demonstrated in the following two Similar Conditions Windows captures.


For Smog Inspectors in California, pay attention to Warm up cycles and Miles Driven.  PID $30 (Warm Up Cycles Since Cleared) and PID $31 (Distance Traveled Since Cleared) are used by the OIS to Pass or Fail a vehicle with a PDTC(s). If the Warm-Up Cycles are 14 or less or the Distance Traveled is less than 200 miles, the OIS will fail the vehicle. If the Warm-Up Cycle is => 15 and the Distance Traveled is => 200 miles, the OIS will pass the PDTC status.

1. This pattern should be used for most BMW vehicles. The differences within this pattern are the methods of EVAP Leak Detection. The system will test if it has a leak detection pump (LDP) after a cold soak start. If it has a Natural Vacuum Leak Detection (NVLD) or Diagnostic Module Tank Leakage (DMTL) pump, EVAP Small Leak monitor tests will run after an extended engine-off time.

2. The procedure listed pertains to the pattern shown above. NOTE: These steps can run out of order depending on the vehicle speed and engine load.




Topics in this section include:

  1. Drive Cycle Pattern 1
  2. Drive Cycle Procedures
  3. Drive Cycle Video

1. This pattern should be used for most 1996-2007 Chrysler and Dodge vehicles. The differences within this pattern are the methods of EVAP Leak Detection.  The system will test after a cold soak start if it has a leak detection pump (LDP). If it has a Natural Vacuum Leak Detection (NVLD) or EVAP System Integrity Module (ESIM) switch, it will test after the end is shut off.

2. The procedure listed pertains to the pattern shown above. NOTE: These steps can run out of order depending on the vehicle speed and engine load.

3. The video was captured while performing the drive cycle on a dynamometer.  The factory scan tool was used to display the inner workings of the Engine Control Module (ECM).  Note: The enable criteria are shown on the scan tool at the top of each screen.  The readiness flag status for this drive cycle is displayed in the middle of the screen.



This drive cycle has been used for many FROD vehicles since 1998. One important note is that it does not mention the O2 Sensor monitor test. Experience has proven that O2 heaters and O2 readiness flags work together. The O2 heater must run and pass before the O2 monitor test will run and flip the readiness flag to Complete! 

Note: for Ford vehicles equipped with Universal Exhaust Gas Sensors (UEGO) a variation of the HEGO step listed below is required. This is covered later in this section. 

Some Ford products have an EVAP Monitor Cold Soak Bypass Timer. An internal timer in the ECM determines Cold Soak. If available, it will be displayed on the OEM side of the scan tool under Current Data/Emissions. If the status is YES, the vehicle has sat long enough to achieve a Cold Soak, allowing the EVAP monitor test to run if the fuel level is correct. If it says No, it is not ready, but it can be bypassed. To Bypass the EVAP Monitor Soak Time Command, turn the key on with the engine off, and perform a MODE $04 Diagnostic Clear, but do not turn the key off. The Cold Soak Bypass Timer will switch from NO to YES. After clearing the information, do not turn the key off; start the engine and follow the abovementioned steps. It is now ready to run the EVAP monitor tests, allowing other monitor's tests to run, providing their enable criteria are met.

The Cold Soak Bypass timer is not available on all Ford vehicles. The only way to be sure is to check the emissions page through the enhanced side of the scan tool.

Topics in this section include:

  1. Drive Cycle Pattern 1
  2. Drive Cycle Procedures
  3. Drive Cycle Catalyst Monitor without EVAP video
  4. Drive Cycle EGR Monitor under deceleration video
  5. Drive Cycle EVAP 0.040" Monitor at cruise video

1. This pattern should be used for many GM vehicles starting in 1996.  It represents the vehicles that run the Catalyst monitor tests at cruise.   It is possible to run the vehicle at a steady cruise to complete the Oxygen sensor and Catalyst monitor tests first and then run the EGR monitor tests.

2. The steps listed pertain to the pattern shown above. NOTE: Depending on the startup engine temperature, vehicle speed, and engine load, these steps can run out of order.

3. This video shows the Catalyst monitor tests running to completion at cruise in steps 9 - 10 in the above pattern.  If the O2 or CAT readiness flag(s) is the only flag(s) not set, warm up the engine and follow this part of the pattern. It was edited to exclude a couple of minutes of steady cruise. Note: Some enable criteria are shown on the scan tool at the top of the screen.  The readiness flag status for this drive cycle is not displayed on the screen.

4. This video shows the EGR monitor tests running to completion after multiple decelerations.  If the EGR readiness flag is the only one not set, then warm up the engine and follow steps 1 - 8 in the above pattern. While watching the video, look closely at the PIDs used to count EGR samples. When the vehicle is accelerating, the system is in non-readiness mode.  When the vehicle is decelerating, the system is in readiness mode. Note: Some enable criteria are shown on the scan tool screen.  The readiness flag status for this drive cycle is not displayed on the screen.

5. This video shows the EVAP 0.040" monitor tests running to completion at steady cruise after a Cold Soak startup.  While watching the video, look closely at the PIDs used to monitor the system for leaks. Note: The actual monitor test is being performed, and the test result is displayed in the middle of the screen below the PIDs.  The readiness flag status for this drive cycle is not displayed on the screen.

Topics in this section include:

  1. Drive Cycle Pattern 2
  2. Drive Cycle Procedures
  3. Drive Cycle Catalyst Idle at cruise video
  4. Drive Cycle EGR Monitor under deceleration video
  5. Drive Cycle EVAP 0.040" Monitor at cruise video
  6. Drive Cycle EVAP 0.020" Engine Off Natural Vacuum (EONV) Monitor video

1. This pattern should be used for many GM vehicles starting in 1998.  It represents a vehicle that runs the Catalyst monitor tests at idle step 12.  It is possible to run the vehicle at a steady cruise to complete the Oxygen sensor and Catalyst monitor tests first and then run the EGR monitor tests.

2. The steps listed pertain to the pattern shown above. NOTE: Depending on the startup engine temperature, vehicle speed, and engine load, these steps can run out of order.

3. This video shows the GM Idle Catalyst monitor test running to completion at idle. It is recommended that full screen be selected for better video quality and clarity. The readiness flag status for this drive cycle is not displayed on the screen. 

4. This video shows the EGR Decel monitor tests running to completion after multiple decelerations.  If the EGR readiness flag is the only one not set, warm up the engine and follow this part of the pattern. While watching the video, look closely at the PIDs used to count EGR samples. Note: Some enable criteria are shown on the scan tool screen.

The following capture shows the GM CAT monitor test running at idle; This data was collected through Global OBDII on a CAN-compliant vehicle. 

This data was collected through Global OBDII on a CAN-compliant vehicle.  

Step 1: The PCM Commands a Lean-to-Rich A/F ratio; the A/F ratio is quickly changed from a Lean Command to Lambda and then to a Rich Command. 

Step 2: The system is now in Open Loop, with no O2 Sensor Feedback Correction through Fuel Trims. 

Steps 3 & 5: The front O2s Sensors respond by indicating a Lean exhaust as the Commanded A/F ratio moves to a Lean A/F ratio, and the front O2 Sensors respond by indicating a Rich Exhaust Condition as the A/F ratio moves to a Rich Command. 

Steps 4 & 6: The rear O2 Sensors respond by indicating that excess oxygen is exiting the CAT. As the A/F ratio command moves Rich, the CAT is slowly depleted of Oxygen, raising the rear O2 Sensor’s voltages. 

The CAT Monitor has now Completed because no DTC is present. MODE $06 test results showed both CATs passing within the Min/Max Parameters. If you understand the enable criteria and the PIDs available, you can set up a custom screen to watch the operation of some monitor tests as they run.

5. This video shows the EVAP 0.040" monitor tests running to completion at steady cruise after a Cold Soak startup.  While watching the video, look closely at the PIDs used to monitor the system for leaks. Note: Some enable criteria are shown on the scan tool screen. The actual monitor test is displayed in the middle of the screen. 

6. This scan tool graphing video shows the EVAP 0.020" very small leak monitor tests running to completion with the engine-off.  

Topics in this section include:

  1. Drive Cycle Pattern
  2. Drive Cycle Procedures
  3. Drive Cycle Video without EVAP
  4. Drive Cycle EVAP Video

1. This pattern should be used for most NISSAN/INFINITI vehicles between 1998 - 2003.  During these years, the EVAP system tested under pressure in Steps 5 & 6.

2. The steps listed pertain to the pattern shown above. NOTE: Depending on the startup engine temperature, vehicle speed, and engine load, these steps can run out of order.

3. This video was captured while performing this drive cycle on a dynamometer.  The factory scan tool at that time displayed the inner workings of the Engine Control Module (ECM).  Pattern 1 does not show Steps 5 & 6 for the EVAP portion of the drive cycle. These steps will be shown in the following video.

4. This video shows NISSAN Pattern 1 Step 5.  Step 6 is only required if the Fuel Temp Sensor does not rise a minimum of 2 degrees Celsius (4 degrees F).  Focus on the Fuel Tank Temperature, Purge VOL, VAC Cut, and Vent solenoids. The OE side of the scan tool will have to be accessed to see these PIDs.  NOTE: The vent solenoid might not be displayed when using an aftermarket scan tool.

Topics in this section include:

  1. Drive Cycle Pattern
  2. Drive Cycle Procedures
  3. Drive Cycle without EVAP Video
  4. Drive Cycle EVAP Video

1. This pattern was used for most NISSAN/INFINITI between 2004 & later vehicles.  During these years, the EVAP system will test under a vacuum in Steps 4 & 5. If the Fuel Tank Temperature Sensor indicates the fuel tank temperature has not increased enough, step 6 will have to be performed.

2. The steps listed pertain to the pattern shown above. NOTE: Depending on the startup engine temperature, vehicle speed, and engine load, these steps can run out of order.

3. This video was captured while performing the drive cycle on a dynamometer.  The factory scan tool at that time displayed the inner workings of the Engine Control Module (ECM). NISSAN Pattern 2 was used for most NISSAN/INFINITI vehicles after 1998.  The main difference after 2003 was with the EVAP system.  The video does not show Steps 5 & 6 in Pattern 2.  Those steps will be shown in the following video.

4. This video shows NISSAN Pattern Steps 4 - 5.  Step 6 is only required if the Fuel Temp Sensor does not rise a minimum of 4⁰ F (2⁰ C).  Performing step 6 multiple times will slosh the fuel in the tank, resulting in a temperature and pressure increase. Focus your attention on the Purge VOL and Vent solenoids.  This system leaks, so the PCM first tests the system using vacuum decay and then proceeds to test the system under pressure.



Topics in this section include:

  1. Drive Cycle Pattern
  2. Drive Cycle Procedures
  3. Drive Cycle without EVAP video
  4. Drive Cycle non-Intrusive EVAP video

1. This pattern should be used for 1996-2000 Toyota and Lexus vehicles. These vehicles were equipped with a non-Intrusive Evaporative Emission System.

2. The steps listed pertain to the pattern shown above. NOTE: Depending on the startup engine temperature, vehicle speed, and engine load, these steps can run out of order.

3. This video was captured while performing the drive cycle on a dynamometer.  The factory scan tool at that time displayed the inner workings of the Engine Control Module (ECM).

4. This video shows the non-Intrusive EVAP monitor tests running to completion at steady cruise after a Cold Soak startup.  While watching the video look closely at the PIDs (Purge, Vapor Pressure, and Vapor Pressure Solenoid); they are used to monitor the system for leaks. Note:  The readiness flag status for this drive cycle is displayed at the bottom of the screen.


Topics in this section include:

  1. Drive Cycle Pattern
  2. Drive Cycle Procedures
  3. Drive Cycle without EVAP video
  4. Drive Cycle non-Intrusive EVAP video

1. This pattern should be used for 2001 and newer Toyota and Lexus vehicles. These vehicles were equipped with an Intrusive or Vacuum Pump Evaporative Emission System.



This section will address some oddities when performing individual monitor tests, separate from running a complete drive cycle.

MORE CONTENT TO BE ADDED; PLEASE CHECK BACK!




This section will cover the following topics:

  • Define the differences between a readiness flag and a monitor test.
  • Present a plan for a driver-seat diagnostic approach to handling incomplete readiness flags for non-continuous monitor tests! 
  • Define In-Use Performance Monitor Numerator (Completions), Denominator (Conditions), and Numerator/Denominator Ratio.
  • Develop an understanding of how GLOBAL OBDII MODES, MODE $09 & MODE $06, can be used to identify why a Readiness Flag won’t Flip to Complete.
  • Discuss a variety of Case Studies applying the techniques covered in this workshop.

What are the differences between a readiness flag and a monitor test?

A Readiness Flag is used to report that a specific emission-related system has completed testing. Each readiness flag can consist of one or multiple individual monitor tests. State emissions programs use some readiness flags as part of an official Inspection, and a minimum number of readiness flags must be Complete to pass the Inspection.

Non-continuous readiness flags can only flip to complete “Once Per Trip” when the enable criteria are met for the following:

  • Catalyst(s)
  • Oxygen & Air Fuel Sensor(s)
  • Heated Oxygen & Air Fuel Sensor(s)
  • EGR and VVT
  • Evaporative Emissions 
  • Secondary Air Injection

A Monitor test is system-specific and can set a Diagnostic Trouble Code (DTC). It should not be associated with only readiness flag status because every DTC has a related monitor test used to pass or fail a system or component. A monitor test applies to both non-continuous and continuous monitor testing. 

The following capture shows a non-continuous monitor test will run once per trip if passing. If the marginal or failing, the ECM will run the test multiple times during the same trip. So, non-continuous readiness flag tests can only complete once per trip, but the monitor test can run multiple times if failing.

The following plan is a driver-seat diagnostic approach to handling incomplete readiness flags for non-continuous monitor tests. 

The most common response for a technician preparing the vehicle for an emissions inspection is: I can't get the monitors to run. The better response should be, I can't get the ............flag to complete. Once the technician understands this, an organized driver-seat systematic approach is needed.

Here is a plan to help organize that systematic approach. The chart can be used on almost all OBD II vehicles. The box below for In-Use Performance Monitor Tracking (IUPMT) provides a history to identify a problematic readiness flag. This should be considered when quoting a price to run and setting one or more readiness flags to complete. 

As you move through this chart, the year of the vehicle and how many readiness flags are set to Not Complete.

Begin by verifying the readiness flag status in MODE $01 for Monitors Since DTCs Last Cleared. The following capture is a red flag that Modified Software is installed because all readiness flags have been disabled and reported as Not Supported. This vehicle has most likely been tuned with an aftermarket tuner, and the readiness flags have been disabled. 

The following capture could have occurred because the memory cleared, the vehicle has been driven such that no enable criteria were met, and more driving is required. It could also be the battery died, Keep-Alive Memory to the ECM lost power was removed, or the ECM was reprogrammed. 

This indicates another approach is required because the O2 Sensor is the only readiness flag needed to pass the Smog Inspection. This could pose a problem and cost time and money.

The following will define In-Use Performance Monitor Completions, Conditions, and Ratios. 

For CAN “C” equipped vehicles, check MODE $09, In-Use Performance Monitor Tracking (IUPMT), to see the frequency with which each readiness flag runs long enough and often enough to detect a failing system or component. IUPMT can provide invaluable information about the success rate for setting each readiness flag.

The word Numerator identifies the Completions. It represents the actual monitoring events where the OEM enable criteria ran long enough that a malfunctioning component or system would have been detected. Regardless, if the readiness flag Passes or Fails, the Numerator will be incremented. The Numerator alone does not indicate the chances of completing a readiness flag or flags.

The word Denominator identifies the Conditions. It represents the number of times the manufacturer has met the CARB criteria and been charged a trip. Meeting CARB criteria establishes a charged trip against the manufacturer. Understand that the Denominator is a measure of vehicle driving activity; it is not a measure of actual monitoring opportunities. The Denominator alone does not indicate the chances of completing a readiness flag or flags. 

Knowing the Completions and Conditions creates an In-Use Performance Monitor Track Ratio (IUPMR). This ratio allows CARB to track the frequency of a readiness flag monitor test runs long enough to detect a failing component or system. Understanding this ratio can be invaluable for the technician when identifying difficult-to-complete readiness flags.

CARB established the below minimum in-use ratios for 2010 and newer vehicles. During the phase-in years of 2007-2009, the In-Use Performance Monitor Ratio requirements were 0.100 for all tracked readiness flags. These are the minimum acceptable ratios established by CARB, but they are not acceptable for the technician. The ratio displayed in MODE $09 on the vehicle gives the technician an idea of the chances of completing a readiness flag or flags.  

The following capture is from a vehicle equipped with a 0.040” EVAP leak detection monitor test. The minimum CARB ratio for a 0.040” EVAP leak detection monitor test is .520 (0.40” Leak). This particular vehicle is well below the minimum acceptable ratio.  

What is the Definition of a CARB Denominator Trip? 

The Catalyst, O2 Sensors, EGR, and VVT Denominators should be incremented only on trips that meet the following CARB Criteria:

  • The total run time for the current trip is >/= 10 minutes,
  • Total run time above 25mph during the current trip is >/= 5 mins,
  • One continuous idle during the current trip is >/= 30 seconds,
  • The elevation is < 8000 feet,
  • Ambient Temperature is > 20⁰ F.
  • Hybrid vehicles, cumulative fueled engine operation >= 10 s

Additional Monitor-Specific CARB Criteria:

  • Secondary AIR also requires a 10-second commanded “ON” signal.
  • At startup, EVAP requires ECT and IAT temperatures to be within approximately 10°F of each other. The ECT temperature must be between 40°- 95°F.

The CARB Trip is comprised of three tests:

  1. Total Propulsion Time 10 minutes.
  2. One continuous 30-second idle.
  3. 5 minutes of accumulated drive time above 25mph.

Only one CARB trip per readiness flag can occur per key cycle!

The following capture shows In-Use Performance Monitor Tracking data. Note that the OBD Monitoring Conditions 745 matches the Catalyst, O2 Sensor, EGR/VVT, and Secondary O2 sensor conditions. While this will not always be the case, they will typically be close.

One readiness flag is not shown in the previous capture; the O2 Heater is omitted. Why not? CARB does not see it as that critical because it is not calibrated to an emission threshold (like a heater performance fault before emissions exceed 1.5x standards); it is just a functional check; is the heater working or not working?

In the following capture, note that the Numerators and Denominators incremented for the Catalyst, O2 Sensors, and EGR. If no DTC is present, it is safe to assume all monitor tests have passed. This shows what happens when an OEM and CARB trip is complete in the same key cycle. The EVAP Numerator and Denominator remained unchanged, indicating it did not meet the definition of an OEM or CARB Trip.

The vehicle in the following capture was equipped with a Key-Off EVAP system. After the key was turned off and the vehicle sat long enough to allow the Key-Off EVAP monitor tests to run and increment the Completions during an OEM trip that did not meet the criteria for a CARB trip. The manufacturer was not charged for a CARB trip, so the Numerator Increased without the Denominator Increasing.

The following capture shows the Completions for the O2 and EGR incremented during many OEM trips that did not meet the criteria of the CARB trip. This could happen for the following reasons:

  • The vehicle is in excellent working order, and the enable criteria are easily met, so readiness flag monitor tests complete more frequently without meeting the requirements for a CARB trip. 
  • The vehicle could be in an EWMA MODE that requires multiple trips. During these trips, the Numerator will increment when the required monitor test runs long enough to detect a Pass/Fail.

Why didn’t the Denominator increment? An example would be starting the vehicle and immediately accelerating to 55mph while cruising the O2/AFS and CAT monitor test run. The technician immediately stops and shuts off the vehicle after five minutes with only four minutes above 25 mph and no thirty-second continuous idle period. Did this trip meet the definition of a CARB Trip? The answer is No. Look back at the criteria for a CARB trip.

What do these readings tell you about your ability to run these monitor tests? The ratios are well over one, indicating that their readiness flags should be easy to flip to Complete.

The following was captured from Ford OBDII Reference Data for Gasoline or Hybrid vehicles to show what DTC(s) will increment the Numerator. If this specific DTC test runs long enough to determine if the system or component could fail, the Numerator will increment. These DTCs are also considered a "Once Per Trip" monitor test. It should be typical of other manufacturers.

Each DTC relates to an individual monitor test. Multiple monitor tests can pass, and the readiness flag remains Not Complete. The following capture shows all the O2 sensor DTCs available on one vehicle. The "Once Per Trip" DTCs highlighted in Green are the DTCs responsible for flipping the readiness flag to complete.   

Learn to quickly scan the MODE $06 MIDs related to the pre and post Oxygen Sensors. If any of TIDs are reporting a Test Result of 0, that is most likely the blocker preventing the readiness flag from flipping to complete. This video demonstrates the technician scanning MODE $06 TIDs because the O2 Sensor flag is incomplete. In this case, it cannot be said that the monitor would not run; many monitor tests have run, but the monitor test required to flip the flag has not run yet.

In this next video, MID $01 and TID $85 shown in the previous video now has run and passed. The readiness flag is now Complete.


MORE CONTENT TO BE ADDED; PLEASE CHECK BACK!



The fuel vapor recovery system was the most neglected part of a vehicle’s emission system, according to the Environmental Protection Agency (EPA).

Automotive fuel systems are not truly sealed. They are vented to maintain pressure as fuel is added or used. Refueling, temperature fluctuations, and evaporation create excess fuel vapor. The Evaporative Emissions System must handle this hydrocarbon (HC) vapor.

Factory emission tests have determined that an EVAP system with a leak as small as .020” can yield an average of 1.35 grams of HC per vehicle driven mile. This is 30 times over the current allowable exhaust emissions standard.

In addition to causing HC emissions, the EVAP system's failure wastes fuel and often creates customer concern about gasoline odors.

This video, without audio, was developed by California Air Resources Board (CARB). It shows actual hydrocarbon vapors created by removing a gas cap, removing the nozzle from the filler next, and filling a container with fuel. These actions are performed daily by millions of people.

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