The knock sensor system enables the PCM to control ignition timing for best performance while protecting the engine from detonation.
The KS system uses one or 2 flat response 2-wire sensors. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration or noise level. The control module receives the KS signal through a signal circuit. The KS ground is supplied by the control module through a low reference circuit. The control module learns a minimum noise level, or background noise, at idle from the KS and uses calibrated values for the rest of the RPM range.
In order to determine which cylinders are knocking, the control module only uses KS signal information when each cylinder is near Top Dead Center (TDC) of the firing stroke. If knock is present, the signal will range outside of the noise channel. If the control module has determined that knock is present, it will retard the ignition timing to attempt to eliminate the knock. The control module will always try to work back to a zero compensation level, or no spark retard.
Removal & Installation
- Remove the starter.
- Disconnect the knock sensor (KS) harness connector.
- Remove the KS retaining bolt.
- Remove the KS.
- Installation is the reverse of removal.
- Turn OFF the ignition.
- Disconnect the knock sensor (KS).
- Measure the resistance from the KS signal circuit terminal A on the sensor side of the KS harness connector to a good ground.
- Measure the resistance from the KS signal circuit terminal B on the sensor side of the KS harness connector to a good ground. If the circuits display an open for both circuits, test for an intermittent and for a poor connection at the KS.
- Turn ON the ignition, with the engine OFF.
- On the Powertrain Control Module (PCM) side of the KS harness connector, measure the DC voltage from the KS signal circuit terminal A to a good ground..
- On the PCM side of the KS harness connector, measure the DC voltage from the KS signal circuit terminal B to a good ground.
- If the voltage more than the 4.2 volts, test the KS signal circuit for a short to voltage.
If there are no issues with the wiring and connectors, replace the sensor.