P0327

P0327 - Knock Sensor (KS) Circuit Low Input




Circuit Description
The PCM uses the Knock Sensor (KS) in order to detect engine detonation. This allows the PCM to retard the Ignition Control (IC) spark timing based on the KS signal the PCM receives. The circuitry within the knock sensor pulls down the PCM-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 A/C signal that rides on the 1.3 volts DC. The signal's amplitude and frequency are dependent upon the amount of the knock being experienced.

The PCM 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 CM 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. Then the ECM determines that an abnormally high noise channel voltage level is being experienced, a Diagnostic Trouble Code P0327 sets. This DTC is a type B DTC.

Conditions for Setting the DTC

A/D Test
The following conditions are met for 7.5 seconds within a 10 second monitoring period:
- Engine speed is equal to or greater than 2000 RPM.
- A/D Voltage is less than or equal to 0.0977 Volts.

Gain Test
The following conditions are met for 7.5 seconds within a 10 second monitoring period:
- Engine speed is greater than 2500 RPM.
- Gain is equal to or greater than 23.875 dB.

Action Taken When the DTC Sets
- The PCM will illuminate the MIL the second time the fault is detected.
- The PCM will store the conditions which were present then the Diagnostic Trouble Code set.
- The PCM will use a calculated spark retard value in order to minimize the knock during the conditions when the knock is likely to occur. The calculated value will vary based on the engine speed and load.

Conditions for Clearing the MIL/DTC
A history Diagnostic Trouble Code will clear after 40 consecutive warm-up cycles have occurred without a fault.
The Tech 2 "Clear Info" will clear the Diagnostic Trouble Code.

Diagnostic Aids
Check for the following conditions:

A poor connection at the PCM. Inspect the knock sensor and the PCM connectors for: broken locks, improperly formed or damaged terminals.
- Backed out terminals
- Broken locks
- Improperly formed or damaged terminals

Also, check the wiring harness for: shorts to ground, shorts to battery positive, and open circuits.
- 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.

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

Step 1:

Steps 2 - 4:

Steps 5 - 8:

Steps 9 - 12:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
2. Ensures that the fault is present.
6. Ensures that the knock sensor is capable of detecting detonation.