P0325

DTC P0325 Knock Sensor (KS) Circuit




Circuit Description
The knock sensor system detects for an engine detonation. The knock sensor produces an AC voltage signal. The amplitude and the frequency of the AC voltage signal is dependent upon the knock level being detected. This signal then travels to the KS module that is an internal part of the PCM. If knock is detected, the PCM will retard the spark timing based on the signal from the knock sensor.

Conditions for Running the DTC
- Engine run time is more than 20 seconds.
- Engine Coolant Temperature (ECT) is more than 56° C (131° F).
- Engine speed is above 1600 RPM.
- MAP is more than 60 kPa.
- Engine vacuum is less than 33 kPa.

Conditions for Setting the DTC
- The KS voltage and variation is not within normally expected ranges.
- The above conditions are present for more than 60 seconds.

Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool's Freeze Frame and Failure Records.

Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22° C (40° F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70° C (158° F) during the same ignition cycle.
- Use the scan tool Clear Information function

Diagnostic Aids
Check and correct any abnormal engine noise before using the diagnostic table.
An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs.

Steps 1 - 2:

Steps 3 - 6:

Steps 7 - 10:

Steps 11 - 12:

Test Description
The numbers below refers to the step numbers on the Diagnostic Table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the this DTC set. The scan tool stores this data for later reference.
2. If the conditions for the test as described above are met, a DTC P0325 will set and the MIL will illuminate.
3. If the engine has an internal knock or an audible noise that causes a knocking type of noise on the engine block, this is an indication that the knock sensor may be responding to the noise.
5. This step checks the internal resistance of the knock sensor or the wiring to the knock sensor.
6. Thoroughly check any circuitry suspected of an intermittent conditions.
7. Program the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communication System (ITCS) information for PCM programming.