Electronic Control System: Self-diagnosis

WARNING: This page is about a different car, the 2006 Acura MDX, 2005 Acura MDX, 2004 Acura MDX, and 2003 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

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 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 the first drive cycle, the PCM stores a Temporary DTC. The MIL does not come on. If the failure continues in the second drive cycle, the PCM stores a DTC and turns on the MIL.