Electronic Spark Control Module: Description and Operation

Knock Sensor System

All gas engines are equipped with a knock sensor system. A knock sensor is mounted on the engine block. On vehicles with a manual transmission, the sensor is connected by a blue wire to the knock sensor module, which is bracket mounted on the top of the engine. The sensor, in response to engine knock, sends a signal to the module and from there to the ECM, located in the passenger compartment. The ECM sends a signal to the distributor to retard timing.

If the vehicle is equipped with an automatic transmission (4L80E or 4L60E), a PCM (powertrain control module) is used instead of an ECM. The PCM performs all ECM functions and also provides electronic control for the transmission. It is located in the same place as the ECM.

NO knock sensor module is used on a vehicle equipped with a PCM. Instead, the blue wire from the knock sensor is wired directly to the PCM.