P0325
Steps 1 - 2:
Steps 3 - 11:
Steps 12 - 14:
DTC P0325 Knock Sensor (KS) Circuit Malfunction
Circuit Description
The knock sensor (KS) system is used to detect engine detonation. The knock sensor produced an AC voltage signal. The knock sensor sends this signal to the PCM. The amplitude and the frequency of the AC voltage signal depends upon the knock level being detected. The PCM will then retard the spark timing based on the signals from the Knock Sensor. DTC P0325 is a type B code.
Conditions for Setting the DTC
- Engine run time is greater than 10 seconds.
- No P0327 Diagnostic Trouble Code set.
- Engine speed is above 2500 rpm.
All the above mentioned conditions are met, and the following conditions are met for 8.75 seconds within a 10 second monitoring period:
- Any of the four AID voltages exceeds 1.5625 Volts.
- Instantaneous AID delta Voltage falls below 0.019531 Volts.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate the second time the fault is detected.
- The PCM will record operating conditions at the time the diagnostic fails.
- A history Diagnostic Trouble Code is stored.
- The PCM will use a calculated spark retard value in order to minimize the knock during the conditions when the knock is likely to occur. The calculated value will vary based on the engine speed and load.
Conditions for Clearing the MIL/DTC
The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
- A history Diagnostic Trouble Code will clear after 40 consecutive warm up cycles without a fault.
- A Scan Tool can clear the Diagnostic Trouble Codes.
Diagnostic Aids
Correct any abnormal engine noise before using the diagnostic table. Check for an open ignition feed circuit.
Steps 1 - 2:
Steps 3 - 11:
Steps 12 - 14:
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data and failure records data on the Scan Tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the Scan Tool for later reference.
2. If the conditions for the test as described above are met, a Diagnostic Trouble Code P0325 will set and MIL will illuminate.
4. If the engine has an internal knock or audible noise that causes a knocking type noise on the engine block, the knock sensor may be responding to the noise.
6. The Scan Tool displays knock sensor activity in counts, approximately 20-50 at idle. The counts should increase when engine speed is increased and the counts should decrease when engine speed is decreased.
7. Any circuitry, that is suspected as causing the complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.
8. If the KS module was previously replaced and the Diagnostic Trouble Code resets, a malfunctioning PCM is indicated.
NOTE: Replacement PCMs must be reprogrammed. Refer to Engine Control Module / Service and Repair.
9. Checking the internal resistance of the knock sensor verifies if the knock sensor or the wiring to the knock sensor is OK.