Q: What is the purpose of the knock sensor and how is it replaced for Chevrolet Colorado and GMC Canyon?
A: The knock sensor detects abnormal vibration (spark knock or pinging) in the engine. The knock control system is designed to reduce spark knock during periods of heavy detonation. This allows the engine to use maximum spark advance to improve driveability. Knock sensors produce an AC output voltage that increases with the severity of the knock. The signal is fed into the PCM and the liming is retarded to compensate for the severe detonation. To replace the sensor, disconnect the cable from the negative battery terminal. Raise the vehicle and place it securely on jackstands. On inline engines, the knock sensor is located on the left side of the block, to the rear of the air conditioning compressor. On V8 engines, there are two sensors: one on each side of the block. Raise the vehicle and support it securely on jackstands. To remove the right sensor on a V8 engine, remove the inner fender splash shield. Disconnect the wiring from the sensor. Remove the sensor bolt and the sensor. Installation is the reverse of removal. Tighten the bolt to 18 ft-lbs.