Circuit Description

Under normal operation, until engine RPM is high enough for the PCM to control spark, PCM will open the bypass circuit to the IC module, the IC module will then ground the IC module circuit. This mode is called the module mode, because the IC module is controlling the spark at his point. Once engine speed is high enough (about 65 RPM), the 4X reference pulses are received and if no PCM faults are detected, PCM will close the bypass line and in response the IC module will unground the IC circuit, allowing PCM to control spark. This mode is called the control mode.

This test is used to check for faults in both the bypass and the IC circuit. To check both circuits, this diagnostic runs 2 tests. One during crank and one while engine is running. If IC control pulses are detected by the PCM on the IC line while in module mode (cranking) or if no ignition control pulses are detected by the PCM while in ignition control mode (running), DTC will set.