Circuit Description
The knock sensors are used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the KS signal being received. The knock sensors produce an AC signal which rides on a 5 volts DC signal supplied by the PCM. The signal amplitude and frequency is dependent upon the amount of knock being experienced.
The PCM determines whether the knock sensors and related wiring are operating properly by monitoring the voltage level on the noise channel. The noise channel allows the PCM to diagnose the KS system by allowing the PCM to learn the amount of normal engine mechanical noise present. Normal engine noise varies depending on engine speed and load. Normal engine noise varies depending on engine speed and load. The PCM contains a replaceable Knock Sensor (KS) module. The KS module contains the circuitry that allows the PCM to diagnose the KS sensors and circuitry. If the KS module is missing or malfunctioning causing a continuous knock condition to be indicated, the PCM will set DTC P0325.
Conditions for Running the DTC
- No TP sensor, VSS, or ECT sensor DTCs are set.
- The engine has been running for at least 10 seconds
- Engine coolant temperature is greater than 65°C (149°F).
- System voltage is greater than 9 volts.
Conditions for Setting the DTC
| • | The PCM detects a problem with the KS module circuitry that causes knock to be indicated continuously. |
| • | Above conditions for up to 2.5 seconds. |
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. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at the PCM -- Inspect KS module connector for backed out terminals, broken locks, and improperly formed or damaged terminals. |
| • | Damaged or improperly installed KS module -- Check for bent pins, deformed terminals, or the KS module not completely seated. |
Review the Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Ensures that the malfunction is present.
-
Checks for an improperly installed KS module.
-
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 ign? | -- | |||
3 |
Does scan tool indicate DTC P0325 test failed this ign? | -- | Refer to Diagnostic Aids | |
4 |
Was a problem found? | -- | ||
Was a problem found? | -- | |||
6 |
Note test result; does scan tool indicate DTC P0325 failed this ign? | -- | ||
Replace the PCM. Important:: The replacement PCM must be programmed. Go to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||
8 |
Does the scan tool indicate DTC P0325 test failed this ign? | -- | System OK |
