Circuit Description
The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. The input signal from the knock sensor is used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the amplitude and frequency of the KS signal being received. The knock sensor produces an AC signal under all engine operating conditions. During engine operation, the PCM calculates the average voltage range of the knock sensor signal. If the knock sensor system is operating normally, the PCM should monitor the KS signal voltage varying over 0.5 volt above and below the calculated average range. If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuit, DTC P0325 will set.
Conditions for Running the DTC
- No AIR, VSS, TP, CKP, MAF, or ECT sensor DTCs set.
- Engine speed is between 1000 and 3000 rpm.
- Throttle angle is greater than 15%.
- Engine load is greater than 45%.
- Engine coolant temperature is greater than 65°C (149°F).
- Maximum spark retard is less than 15 degrees.
- System voltage is greater than 9 volts.
- Engine run time greater than 30 seconds.
Conditions for Setting the DTC
The PCM detects a malfunction in the integrated knock sensor diagnostic circuitry which will not allow proper diagnosis of the knock sensor circuit.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
The PCM will use a calculated spark retard value to minimize knock during conditions when knock is likely to occur. The calculated value will vary based on engine speed and load.
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL Off after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A last test failed (current DTC) clears when the diagnostic runs and does not fail. |
| • | A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. |
| • | Use a scan tool in order to clear the MIL/DTC. |
| • | Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module (PCM) Description , Clearing Diagnostic Trouble Codes. |
Diagnostic Aids
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
• The PCM harness connectors • The electrical center fuse/relay cavities • The component terminals • The component harness connector
If the problem is intermittent, refer to Intermittent Conditions .
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Was a problem found and corrected? | -- | ||
Replace the PCM. Important:: The replacement PCM must be programmed. Go to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
4 |
Does the scan tool indicate that this test ran and passed? | -- | ||
5 | Review Captured Info using the scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to the applicable DTC table
| System OK |
