Fuel and Emissions System Description - Electrical Control System
Electronic Control System
The functions of the fuel and emission control systems are managed by the engine control module (ECM) on vehicles with manual transmissions or the powertrain control module (PCM) on vehicles with automatic transmissions.
Self-diagnosisThe ECM/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 either the first or the second drive cycle. When a DTC is stored, the ECM/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 ECM/PCM stores a DTC for the failure in the RAM 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 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 ECM/PCM stores a DTC in erasable memory and turns on the MIL.