System Diagnosis - Knock Sensor (KS)

KNOCK SENSOR
The self check used by the control module monitors the voltage on the Knock Sensor (KS) circuit and if the voltage is below about 0.4 or over about 4.6, a DTC P0327 sets.

Knock Sensor (KS) DTCs: DTC P0327 A DTC set when system is in a self check, and voltage on the KS circuit is above or below the specified range. Refer to the applicable table.

CIRCUIT DESCRIPTION
The Knock Sensor detects engine detonation. The Vehicle Control Module (VCM) retards the electronic spark timing based on the signal being received. The Knock Sensor produces an AC signal. The amplitude and frequency are dependent upon the knock level. The KS module sends a signal to the VCM. The VCM then retards the spark timing in order to reduce the detonation.

DIAGNOSTIC AIDS
While observing the knock signal on the scan tool, there should be an indication that a knock is present whenever a knock can be heard. Engine knock is most likely to occur under high engine load conditions.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

1. The OBD System Check prompts the technician to store the Freeze Frame Data in the scan tool. This will create an electronic copy of the freeze frame data taken when the fault occurred that can be referred to later.

2. If the engine has an internal problem which is creating a knock, the Knock Sensor may be responding to the mechanical noise.

3. The scan tool displays Knock Sensor activity in counts approximately 16-22 at idle. The counts should rise when the engine speed increases and the counts should decrease when the engine speed decreases.

5. This checks that the internal resistance of knock sensor is within an acceptable range.

7. Check the Knock Sensor connections for loose terminals or corrosion.