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 Frequency
DTC P0328: Knock Sensor (KS) Circuit High Frequency
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
KS Sensor Signal High | P0325, P0327 | P0325, P0328 | P0325, P0328 | -- |
KS Sensor Signal Low | -- | P0325, P0328 | P0325, P0328 | -- |
Circuit/System Description
The knock sensor (KS) is non-resonant design that is constructed of a piezoelectric element which generates an AC signal when vibrated. Normal engine operation will cause the KS to generate signals of known frequencies. When engine knock is present, the KS frequency changes. This signals the powertrain control module (PCM) to retard ignition timing. The PCM sends a bias voltage of 5 volts to the KS on the KS Signal High circuit. The PCM expects approximately 2.5 volts back on the KS Signal Low circuit. The KS generated AC signal rides on top of the bias voltage provided by the PCM. The circuits between the KS sensor and the PCM consist of the following circuits:
| • | A KS signal |
| • | A low reference |
| • | A shielded ground |
Conditions for Running the DTC
P0325
| • | First condition--the engine running |
| • | Second condition--the vehicle speed sensor (VSS) and the throttle position (TP) sensor indicate that the vehicle is accelerating with the engine speed greater than 2,000 RPM |
| • | DTC P0325 runs continuously once the above conditions have been met. |
P0327 and P0328
| • | The ignition is ON or the engine is running. |
| • | DTC P0327 and P0328 run continuously once the above condition has been met. |
Conditions for Setting the DTC
P0325
| • | First condition--The KS signal circuit is less than 0.5 volts for greater than 10 seconds. |
| • | Second condition--The KS signal circuit is greater than 4.5 volts for greater than 10 seconds. |
P0327
The KS signal circuit is less than 0.5 volts for greater than 10 seconds.
P0328
The KS signal circuit is greater than 4.5 volts for greater than 10 seconds.
Action Taken When the DTC Sets
| • | DTC P0325, P0327, and P0328 are Type A DTCs. |
| • | The PCM enters the Fail-Safe function and defaults to maximum spark retard values. |
Conditions for Clearing the DTC
DTC P0325, P0327, and P0328 are Type A 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. |
| • | Engine acceleration will be compromised and AT downshifts delayed when operating in the Fail-safe mode. |
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 OFF, test for less than 10 ohms between the low reference circuit terminal 1 and ground G104.
- Ignition ON, test for 5 volts between the KS signal high circuit terminal 2 and ground.
- If all circuits test normal, test or replace the KS sensor.
Important: If the KS lead is damaged in any way, replace the KS.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit tests normal, replace the PCM. |
| ⇒ | If less than the specified range, test the signal high circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM. |
| ⇒ | If greater than the specified range, test the signal high circuit for a short to voltage. If the circuit tests normal, replace the PCM. |
Component Testing
- Ignition OFF, disconnect the harness connector at the KS sensor.
- Test for 195k-205k ohms at 20°C (68°F) between the KS signal high circuit terminal 2 and the KS signal low circuit terminal 1.
| ⇒ | If not within the specified range, replace the KS sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for control module replacement, setup, and programming |
