P0327

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The VCM uses the Knock Sensors (KS) in order to detect engine detonation. This allows the VCM to retard the Ignition Control (IC) spark timing based on the KS signal which the VCM receives. The circuitry within the knock sensor pulls down the VCM-supplied 5 volt signal, so that under a no knock condition the signal on the KS circuit measures about 1.3 volts. The knock sensors produce an AC signal that rides on the 1.3 volts DC. The amplitude and frequency of the AC signal are dependent upon the amount of the knock being experienced.

The VCM determines whether the knock is occurring by comparing the signal level on the KS circuit with a voltage level on the noise channel. The noise channel allows the VCM to reject any false knock signal by indicating the amount of normal engine mechanical noise present. The normal engine noise varies depending on the engine speed and load. When the VCM determines that an abnormally high noise channel voltage level is being experienced, a DTC P0327 sets.

CONDITIONS FOR SETTING THE DTC

Knock Sensor Update Test

^ The timing retard is no more than 0 degrees.

^ System voltage is greater than 10 volts but no more than 17.1 volts

^ The Engine Coolant Temperature sensor is greater than 60°C (140°F)

^ Engine run time is greater than 2 minutes

^ Engine speed is between 500 RPM and 900 RPM

^ Knock Sensor is less than 3 counts

Active Noise Channel Test

^ No ECT DTCs

^ No TP sensor DTCs

^ The Knock Sensor update test is complete

^ The ECT is at least 60°C (140°F)

^ The engine speed is greater than or equal to 2000 RPM and less than 3000 RPM

^ The TP is at least 5.9%

ACTION TAKEN WHEN DTC SETS

^ The VCM will not illuminate the MIL

^ The VCM will store the conditions which were present when the DTC set as a Fail Records data only. This information will not store as Freeze Frame Data.

^ The VCM will use a calculated spark retard value in order to minimize the knock during the conditions when the knock is most likely to occur. The calculated value will vary based on the engine speed and load.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

Check for the following conditions:

^ A poor connection at the VCM. Inspect the knock sensor and the VCM connectors for the following items:

- Backed out terminals

- Broken locks

- Improperly formed or damaged terminals

^ A misrouted harness. Inspect the knock sensor harness in order to ensure that it is not routed too close to high voltage wires such as spark plug leads.

^ Improper Knock Sensor torque specification. Torque the Knock Sensor to 19 N.m (14 lbs. ft). Refer to Fastener Notice in Cautions and Notices.

Review the Fail Records vehicle mileage since the diagnostic test last tailed in order to help determine how often the conditions that caused the DTC to set occur. This may assist in diagnosing the condition.

TEST DESCRIPTION

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

2. Ensures that the fault is present.

6. Ensures that the knock sensor is capable of detecting detonation.