Electronic Control System: Self-diagnosis

The PCM detects a failure of a signal from a sensor or from another control unit and stores a Temporary DTC or a DTC in erasable memory (RAM). Depending on the failure, a DTC is stored in the first or the second drive cycle. When a DTC is stored, the PCM turns on the malfunction indicator lamp (MIL) by supplying ground to the MIL circuit.

• One Drive Cycle Detection Method 

  When an abnormality occurs in the signal from a sensor or from another control unit, the PCM stores a DTC for the failure in the RAM and indicates the MIL immediately.

• Two Drive Cycle Detection Method 

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