If you want to verify a repair, turn off a Malfunction Indicator Lamp (MIL) without resetting the memory. Viewing the Readiness Flag Status Complete for Drive Cycle is an option. This is called PID $41 "Monitors Complete this Drive Cycle". At each key-on, all readiness flags will display as Incomplete. Once the monitor tests required to flip the readiness flag to complete run and pass, the status will be updated to COMPLETE for this drive cycle. If any readiness flag remains INCOMPLETE, the monitor test(s) required to flip that flag did not run and/or complete. 

Note: this option is only available while connected to a CAN-equipped system. Once readiness flags are COMPLETE for pre-CAN vehicles, the memory must be cleared, setting them back to Incomplete. The vehicle can now be driven to reset the flags to Complete. 

One crucial step that is overlooked because most scan tools do not prompt you is to start the vehicle. Once the vehicle is started, the Readiness Flag Status can now be updated for this drive cycle.

The following prompt is from an INNOVA 7111 tablet.

Unfortunately, most scan tool manufacturers do a poor job of reporting the Enable/Disable for this key cycle. Snap-On scan tools support it, but it is located in MODE $06 for the specific monitor test. 

The following capture shows the O2 Sensors as Incomplete Since Cleared, Enabled, and not having run this key cycle.

The following capture shows the Catalyst and VVT as Complete Since Cleared, Enabled, and not having run this key cycle.

The following capture shows the Catalyst and EVAP Large Leak as Complete Since Cleared, Disabled, and not having run this key cycle.

The following capture shows the O2 Sensors as Complete Since Cleared, Enabled, and it has completed this key cycle.

The following capture shows the EVAP Incomplete Since Cleared, Disabled, and has not run this key cycle.

The image above shows "No," "No," and "No." Does this mean the EVAP monitor tests cannot run? There are always exceptions to the rules. If you are working on a Nissan or Infiniti vehicle, the EVAP monitor tests may still run during the current trip. Why? These systems are equipped with a Fuel Temperature Sensor (FTS) inside the fuel tank. These systems do not require a cold soak or startup to run EVAP monitor tests. The computer monitors the FTS for a 4°F increase. Once it increases by 4°F, it indicates a pressure increase in the tank, enabling the EVAP monitor tests to run.

It is also possible to observe the same status when testing EVAP systems that use a vacuum pump to test for a very small leak with the engine off.

Why will a Readiness Flag be Disabled?  Typical examples are: 

• Engine-off soak not long enough (e.g., cold start temperature conditions not satisfied). 
• Monitor test maximum time limit has been exceeded. 
• Ambient air temperature too low or too high.
• BARO indicated high altitude (8000ft and above).
• For EVAP, the ambient temperature is not between 40°F and 95°F, and/or the IAT and ECT differential is more than 10°F
• Fuel level is too low. Typically, under 15%.

This screen was captured from an INNOVA SDS43 Tablet. At key-on, EVAP and O2 are Disabled for this trip. For EVAP, it is most likely due to the ambient temperature being out of range, either too cold or too hot. But the Disabled Oxygen Monitor is not specified.

When a Readiness Flag reports Disabled, attempting to complete it during this key cycle may be impossible. Is it possible for a disabled readiness flag status to eventually be completed?  The answer is yes, in rare cases. For example, if the vehicle is driven from a low altitude to a high altitude, the readiness flag could flip from enabled to disabled. The readiness flag should not change from disabled to enabled if the conditions change back during the same trip.  

The following capture shows the O2 Readiness Flag Disabled for the current trip. Follow the chart and look at the status switch from disabled to enabled.  While this is not the norm, explaining why is difficult. Reviewing the Global OBDII information did not provide a clue to explain why it is disabled. The only explanation is that something in the OEM program is triggering this status.

The following video shows how to check IM Readiness Status. It will show the Readiness Flag Status since the memory was last cleared. It will also show IM Readiness Status for this drive cycle (PID $41).

How to access Monitors Complete this Drive Cycle (PID $41) https://youtu.be/gecNp9Z7ii0

The following videos were recorded using an HP Tuner (www.HPTuner.com). This is an excellent example of what happens when PID $41 is combined with MODE $01 PIDS. The videos show when the O2 and CAT monitor tests are completed and the enabling criteria that led to their completion. After watching the video, look back at the point when the actual monitor tests were completed. The data was collected from a 2018 Nissan Rogue.

2018 Nissan Rogue O2 Readiness Flag Completion https://youtu.be/iOpiIDQCUnk

2018 Nissan Rogue Catalytic Converter Readiness Flag Completion https://youtu.be/gR9vkDf4HXU

Check back for more information that will be added soon!