Diagnostic Instructions
DTC Descriptor
DTC P0325: Knock Sensor (KS) Circuit
Diagnostic Fault Information
Circuit
| Short to Ground
| High Resistance
| Open
| Short to Voltage
| Signal Performance
|
Knock Sensor Signal
| 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. 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 control module receives the KS signal through 2 isolated signal circuits. The control module adjusts the spark timing based on the amplitude
and the frequency of the KS signal.
Conditions for Running the DTC
DTC P0325 runs continuously when:
| • | The engine speed is equal to or greater than 1,800 RPM. |
| • | The engine coolant temperature (ECT) is greater than -40°C (-40°F). |
| • | The engine run time is greater than 1 second. |
Conditions for Setting the DTC
The KS signal circuits are open or shorted together for 6 seconds.
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
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition ON, engine OFF.
- Disconnect the KS harness connector.
- Measure for 3-5 volts between each of the following circuits and ground on the engine control module (ECM) side of the harness connector.
| • | 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. |
- If the circuits test normal, replace the KS.
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.
Important: DO NOT tap on plastic engine components.
- 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.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
