Cobalt P0327: Understanding the Knock Sensor Circuit

Troubleshooting the Cobalt P0327 Knock Sensor Circuit Low Voltage Code

A Chevrolet Cobalt P0327 is a Knock Sensor (KS) Circuit Low Voltage trouble code. The knock sensor (KS) provides feedback to the ECM so it can control ignition timing to get the best engine performance without detonation. The KS is located on the intake manifold. When a knock occurs, the KS produces an AC voltage that varies based on the severity of the detonation. When the ECM detects knock, it retards ignition timing until the knock is no longer present. The P0327 trouble code is a continuous code, which means the testing runs the entire time the engine is running.

Cobalt knock sensor

Possible causes of Cobalt P0327

Faulty knock sensor or physical damage
Faulty knock sensor wiring
Knock sensor improperly torqued to intake manifold
Knock sensor mounting surface is not free of burrs, dirt, thread sealant.

How to diagnose Cobalt P0327

Locate the knock sensor connector and disconnect it

Using a digital voltmeter, turn the IGN to ON and test each terminal in the connector, connecting one meter lead to one terminal and the other lead to a good ground. Each terminal should read 2-5 volts. If you don’t see that result, check the wiring harness for an open between the connector and the ECM, a short to ground, or wires shorted together.

If the voltage is within spec and the sensor is not damaged and is properly torqued, replace the knock sensor.

The most common causes of Cobalt P0327

Faulty knock sensor
Knock sensor wiring harness rub-through as wiring harness passes by the oil filter housing.

©, 2020 Rick Muscoplat