Electronic Control System: Self-diagnosis

The ECM detects a failure of a signal from a sensor or from another control unit and stores a Temporary DTC or a DTC. Depending on the failure, a DTC is stored in the either first or the second drive cycle. When a DTC is stored, the ECM 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 ECM stores a DTC and turns on the MIL.

• 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 stores a Temporary DTC. The MIL does not come on at this time. If the failure continues in the second drive cycle, the ECM stores a DTC and turns on the MIL.