Circuit Description
The powertrain control module (PCM) contains integrated knock sensor (KS) diagnostic circuitry. Input signals from the knock sensors are used to detect engine detonation, allowing the PCM to retard ignition control (IC) spark timing based upon the amplitude and frequency of the KS signal being received. The knock sensors produce an AC signal under all engine operating conditions. During operation, the PCM calculates an average voltage of each knock sensor's signal and takes instantaneous signal voltage readings. To determine the state of the knock sensor circuitry, the PCM compares the instantaneous signal voltage readings to the calculated average voltage. If the knock sensor system is operating normally, the PCM should monitor instantaneous KS signal voltages readings varying outside a voltage range above and below the calculated average voltage. If a malfunction occurs which does not allow the PCM to diagnose the knock sensor system, DTC P0325 is set. Refer to Knock Sensor (KS) System Description for further information.
Conditions for Running the DTC
- None of the following DTCs are set:
- The engine speed is between 1000 and 4000 RPM.
- The throttle angle is more than 3%.
- The engine load is more than 20%.
- The ECT is more than 75°C (167°F).
- The maximum spark retard is less than 15 degrees.
- The system voltage is more than 9 volts.
| • | Throttle position (TP) sensor DTCs |
| • | Vehicle speed sensor (VSS) DTCs |
| • | Crankshaft position (CKP) sensor DTCs |
| • | Mass air flow (MAF) sensor DTCs |
| • | Engine coolant temperature (ECT) sensor DTCs |
Conditions for Setting the DTC
| • | The PCM detects a malfunction in the integrated KS diagnostic circuitry which does not allow proper diagnosis of the KS circuits. |
| • | The above condition is present for at least 1 second. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM stores the conditions which were present when the DTC set as Fail Records data only. This information is not stored as Freeze Frame data. |
| • | The PCM uses a calculated spark retard value to minimize knock during conditions when knock is likely to occur. The calculated value varies based upon the engine speed and load. |
Conditions for Clearing the MIL/DTC
| • | A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table.
-
Ensures that the malfunction is present.
-
This vehicle is equipped with a powertrain control module (PCM) which utilizes an electrically erasable programmable read-only memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
|
Important:: If an engine knock can be heard repair the engine mechanical problem before proceeding with this diagnostic. Refer to Engine Noise Diagnosis in Engine Mechanical.
Does the scan tool indicate that DTC P0325 Failed This Ign? | -- | |||
3 |
Does scan tool indicate that DTC P0325 Failed This Ign? | -- | Go to Diagnostic Aids | |
|
Important:: The replacement PCM must be programmed. Go to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- | ||
5 |
Does the scan tool indicate that DTC P0325 Failed This Ign? | -- | System OK |
