Electronic Control Systems: Self-diagnosis

The ECM/PCM detects the failure of a signal from a sensor or from another control unit and stores a Pending DTC or a Confirmed DTC. Depending on the failure, a Confirmed DTC is stored in either the first or the second drive cycle. When a Confirmed DTC is stored, the ECM/PCM turns on the malfunction indicator lamp (MIL) by a signal to the gauge control module via F-CAN.

• One Drive Cycle Detection Method 

  When an abnormality occurs in the signal from a sensor or from another control unit, the ECM/PCM stores a Confirmed DTC for the failure and turns on the MIL immediately.

• Two Drive Cycle Detection Method 

  When an abnormality occurs in the signal from a sensor or from another control unit in the first drive cycle, the ECM/PCM stores a Pending DTC. The MIL does not come on at this time. If the failure continues in the second drive cycle, the ECM/PCM stores a Confirmed DTC and turns on the MIL.