Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0325: Knock Sensor (KS) CircuitDTC P0327: Knock Sensor (KS) Circuit Low Voltage
DTC P0328: Knock Sensor (KS) Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
KS Signal | P0327 | P0325 | P0328 | -- |
Low Reference | P0327 | -- | P0328 | -- |
Circuit/System Description
The knock sensor (KS) enables the engine control module (ECM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The ECM adjusts the spark timing based on the amplitude and the frequency of the KS signal. The ECM receives the KS signal through a signal circuit. The ECM supples a ground circuit to the KS through a low reference circuit. The ECM also supplies a shielded ground circuit to the KS. The ECM learns a KS noise level at idle and uses calibrated values for the rest of the engine speed range. The ECM should monitor a normal KS signal within the noise channel.
Conditions for Running the DTC
P0325
| • | The engine speed is between 600-2,900 RPM. |
| • | The airflow into the engine is greater than 40 mg/cylinder. |
| • | DTC P0325 runs continuously once the above conditions are met. |
P0327 and P0328
| • | The engine speed is between 600-8,500 RPM. |
| • | DTCs P0327 and P0328 run continuously once the above condition is met. |
Conditions for Setting the DTC
P0325
The ECM detects the KS signal circuit is open for greater than 5 seconds.
P0327
The ECM detects the KS signal circuit is shorted to ground for greater than 5 seconds.
P0328
The ECM detects the KS signal circuit is shorted to voltage for greater than 5 seconds.
Action Taken When the DTC Sets
DTCs P0325, P0327, and P0328 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0325, P0327, and P0328 are Type B DTCs.
Diagnostic Aids
The following conditions could also set this DTC:
| • | 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
Description and Operation
Knock Sensor (KS) System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Engine running, observe the DTC information with a scan tool. DTC P0325, P0327, or P0328 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the KS.
- Ignition ON, test for 1-2 V between the low reference circuit terminal 2 and ground.
- Ignition ON, test for 2.5-3.5 V between the signal circuit terminal 1 and ground.
- If all circuits test normal, test or replace the KS sensor.
| ⇒ | If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
