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 Descriptors
DTC P0325: Knock Sensor (KS) CircuitDTC P0326: Knock Sensor (KS) Performance
DTC P0327: Knock Sensor (KS) Circuit Low Voltage
DTC P0328: Knock Sensor (KS) Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Knock Sensor Signal | P0327, P0328 | P0325 | P0325 | P0327, P0328 | P0326 |
Circuit/System Description
The knock sensor (KS) system 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 is located on the intake side of the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The ECM receives the KS signal through 2 isolated signal circuits. The ECM adjusts the spark timing based on the amplitude and the frequency of the KS signal.
Conditions for Running the DTC
P0325
This DTC runs continuously when:
| • | The engine speed is greater than 1,500 RPM. |
| • | The engine coolant temperature (ECT) is greater than -40°C (-40°F). |
| • | The engine run time is greater than 1 second. |
| • | DTCs P0327 or P0328 are not set. |
P0326
This DTC runs continuously when:
| • | The engine speed is greater than or equal to 575 RPM. |
| • | The manifold absolute temperature (MAP) is greater than 10 kPa. |
| • | DTCs P0120, P0121, P0122, or P0123 are not set. |
P0327, P0328
This DTC run continuously when:
| • | The ECT is greater than -40°C (-40°F). |
| • | The engine run time is greater than 1 second. |
Conditions for Setting the DTC
P0325
The KS signal circuits are open or shorted together for 6 seconds.
P0326
| • | The KS signal indicates an excessive engine knock is present. |
| • | The ECM commanded spark retard at a given engine load and speed is more than the calibrated value. |
| • | The above conditions exist for 6 seconds. |
P0327 and P0328
The KS signal circuits are shorted to ground or power.
Action Taken When the DTC Sets
DTC P0325, P0326, P0327, and P0328 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTC P0325, P0326, P0327, and P0328 are Type B DTCs.
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. |
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 Testing
P0325, P0327 and P0328
- Ignition ON, engine OFF.
- Disconnect the KS harness connector.
- Measure for 2-5 volts between each of the following circuits and ground on the engine ECM side of the harness connector:
- If the circuits test normal, replace the KS.
Note: If the KS lead is damaged in any way, replace the KS.
| • | The KS signal circuit, terminal A |
| • | The KS signal circuit, terminal B |
| ⇒ | If less than the specified range, test the circuits for a short to ground or an open/high resistance. If the circuits test normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the circuits for a short to voltage. If the circuits test normal, replace the ECM. |
P0326
| Note: If DTC P0327, P0328, P0335, P0336 are also set, diagnose those DTCs first. |
| • | 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 terminal A to the KS signal circuit terminal B on the sensor side of the KS harness connector.
- 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.
Note: DO NOT tap on plastic engine components.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
