DTC Descriptors
DTC P0325: Knock Sensor (KS) Module PerformanceDTC P0326: Knock Sensor (KS) Performance
DTC P0327: Knock Sensor (KS) Circuit Bank 1
DTC P0332: Knock Sensor (KS) Circuit Bank 2
Diagnostic Fault Information
Important: Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Knock Sensor Signal | P0327, P0332 | P0325 | P0325 | P0327, P0332 | P0326 |
Low Reference | P0327, P0332 | P0325 | P0325 | P0327, P0332 | P0326 |
Circuit/System Description
The knock sensor (KS) system enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. Both KS are located under the intake manifold. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The control module adjusts the spark timing based on the amplitude and the frequency of the KS signal. The control module receives the KS signal through a signal circuit. The KS ground is supplied by the control module through a low reference circuit. The control module learns a minimum KS noise level at idle and uses calibrated values for the rest of the RPM range. The control module should monitor a normal KS signal within the noise channel.
Conditions for Running the DTC
| • | DTCs P0326 runs continuously when the engine speed is greater than 800 RPM and manifold absolute pressure (MAP) is greater than 42 kPa. |
| • | DTCs P0325, P0327, and P0332 run continuously when the ignition is ON or the engine is running. |
Conditions for Setting the DTC
P0325
The control module has detected an internal circuitry fault.
P0326
| Important: If DTCs P0335 or P0336 are also set, diagnose those DTCs first. |
| • | The KS signal indicates a noisy engine component (e.g. loose bracket, noisy lifter). |
| • | The control module commanded spark retard at a given engine load and speed is more than the calibrated value. |
| • | The above conditions exist for 5 seconds. |
P0327 and P0332
The KS signal circuits are shorted to ground or power.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | Inspect the KS for physical damage. A KS that is dropped or damaged may cause a DTC to set. |
| • | Inspect the KS for proper installation. A KS that is loose or over torqued may cause a DTC to set. The KS should be free of thread sealant. The KS mounting surface should be free of burrs, casting flash, and foreign material. |
| • | The KS must be clear of hoses, brackets, and engine electrical wiring. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Testing
P0325
This DTC indicates an internal control module circuitry failure. Replace the ECM.
P0327 and P0332
- Disconnect the KS inline connector at the back of the engine.
- Turn ON the ignition with the engine OFF. On the ECM side of the connector, measure for less than 3 volts between the KS signal circuit and a good ground, and between the KS low reference circuit and a good ground.
- Turn OFF the ignition. Test for a short to ground on the signal circuit and the low reference circuit on the ECM side of the connector and the sensor side of the connector.
- Connect the KS inline connector. Disconnect the ECM connector that contains the KS circuits.
- Connect a DMM from the affected KS signal circuit to a good ground and tap on the engine block while observing the signal on the DMM. The DMM should display a fluctuating frequency while tapping on the engine block.
- Connect a DMM from the affected KS low reference circuit to a good ground and tap on the engine block while observing the signal on the DMM. The DMM should display a fluctuating frequency while tapping on the engine block.
| ⇒ | If either circuit measures more than 3 volts, repair the short to voltage in that circuit. |
| ⇒ | If there is a short to ground, repair as necessary. |
Important: Set the DMM to the 400 mV AC Hertz scale and allow the DMM to stabilize to zero before proceeding with the test.
Important: DO NOT tap on any plastic engine parts.
| ⇒ | If the DMM does not show a fluctuating frequency while tapping on the engine block for either circuit, test for an open circuit or for a faulty knock sensor. |
| ⇒ | If the DMM does show a fluctuating frequency while tapping on the engine block for both circuits, replace the ECM. |
P0326
| • | Inspect for a loose or broken vehicle accessory or accessory bracket. |
| • | Inspect for excessive engine mechanical noise. |
Component Testing
- Connect the DMM from the KS signal circuit to the KS low reference circuit at the sensor.
- Set the DMM to the 400 mV AC hertz scale and wait for the DMM to stabilize at 0 Hz.
- Tap on the engine block with a non-metallic object near the KS while observing the signal indicated on the DMM.
- The DMM should display a fluctuating frequency while tapping on the engine block.
Important: DO NOT tap on plastic engine components.
Repair Instructions
Important: Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
