Circuit Description
The 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 on the amplitude and frequency of the KS signal being received. The knock sensors produce an AC signal under all engine operating conditions. The PCM calculates an average voltage of each knock sensor's signal and takes instantaneous signal voltage readings. The PCM uses the instantaneous signal voltage readings to determine the state of the knock sensor circuitry. If the knock sensor system is operating normally, the PCM should monitor instantaneous KS signal voltage readings varying outside a voltage range above and below the calculated average voltage. If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuits, DTC P0325 will set.
Conditions for Running the DTC
| • | No TP sensor, VSS, CKP, MAF, or ECT DTCs are set. |
| • | Engine speed is between 1000 and 4000 rpm. |
| • | Throttle angle is greater than 3%. |
| • | Engine load is greater than 20%. |
| • | Engine coolant temperature is greater than 75°C (167°F). |
| • | Maximum spark retard is less than 15 degrees. |
| • | System voltage is greater than 9 volts. |
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 circuits.
Action Taken When the DTC Sets
| • | The PCM will not illuminate the Malfunction Indicator Lamp (MIL). |
| • | The PCM will store conditions which were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data. |
| • | 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
| • | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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Ensures that the malfunction is present.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
|
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.
Note test result; does scan tool indicate DTC P0325 failed this ignition? | -- | |||
3 |
Does scan tool indicate DTC P0325 test failed this ignition? | -- | Go to Diagnostic Aids | |
|
Important:: The replacement PCM must be programmed. Go to Powertrain Control Module Replacement/Programming . Replace the PCM. Is action complete? | -- | -- | ||
5 |
Does the scan tool indicate DTC P0325 test failed this ignition? | -- | System OK |
