Chart C5 - Electronic Spark Control (ESC) Check

Electronic Spark Control (ESC) is accomplished with a module that sends a voltage signal to the ECM. As the knock sensor detects engine knock, voltage from the ESC module to the ECM is shut off. This signals the ECM to retard timing, if engine speed is over 900 rpm.

1. If a Code 43 is not set, but a knock signal is indicated while running at 1500 rpm, listen for an internal engine noise. Under a no load condition, there should not be any detonation, and if knock is indicated, an internal engine problem may exist.
2. Usually a knock signal can be generated by tapping on the right exhaust manifold. This test can also be performed at idle. Test No. 1 was run at 1500 rpm, to determine if a constant knock signal was present, which would affect engine performance.
3. This will test whether the knock signal is due to the sensor, a basic engine problem, or the ESC module.
4. If the module ground circuit is faulty, the ESC module will not function correctly. The test light should light indicating the ground circuit is okay.
5. Using a test light with 12 volts at circuit No. 496 should generate a knock signal to determine whether the knock sensor is faulty, or the ESC module can't recognize a knock signal.