Self-Diagnostic System: Notes

Engine Control Module (ECM) monitors performance of engine for misfires, catalyst efficiency, exhaust leaks and evaporative control loss. If a fault occurs, the ECM stores a relevant fault code and notifies driver of component failure by illuminating Malfunction Indicator Light (MIL) located in instrument cluster. If ECM detects a fault during its engine operation, it will be caused by one of the following:

• Minimum value of a component signal has been exceeded.
• Maximum value of a component signal has been exceeded.
• Component signal is not present or has not been detected.
• An improbable condition has been diagnosed.

By analyzing various input signals system sensors, ECM detects system failures related to ignition, fueling or exhaust systems. ECM stores Diagnostic Trouble Codes (DTCs) associated with a detected failure until diagnostic system is cleared. When a relevant fault is detected, the fault condition is stored in the ECM memory.

The ECM retains in memory the positions of the crankshaft and the camshaft when the engine is turned off. This allows immediate sequential fuel injection and ignition timing during engine cranking. This information is erased if battery voltage is too low (dead battery). When battery power is reconnected, the immediate sequential fuel injection and ignition timing are disabled for first engine start.