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. During engine operation, the PCM calculates the average voltage of each knock sensors signal. If the knock sensor system is operating normally, the PCM should monitor KS signal voltages varying over 0.5 volt 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 more than 3 percent. |
| • | Engine load is more than 20 percent. |
| • | Engine coolant temperature is more than 75°C (167°F). |
| • | Maximum spark retard is less than 15 degrees. |
| • | System voltage is more 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. |
| • | Above conditions for at least 1 second. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM or knock sensor 1 -- Inspect knock sensor 1 and PCM connectors for backed out terminals, broken locks, and improperly formed or damaged terminals. |
| • | Misrouted harness -- Inspect the knock sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers 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 | 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 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. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
5 |
Does the DTC reset? | -- | System OK |
