P0325

DTC P0325 Knock Sensor 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 greater than 20 seconds.
- Engine Coolant Temperature (ECT) is greater than 56 °C (131 °F).
- Engine speed is above 1600 RPM.
- MAP is greater 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 greater than 60 seconds.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM will record operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
- A history DTC is stored
- The PCM will default to a more conservative spark timing.

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 DTC will clear after 40 consecutive warm up cycles without a fault
- A scan tool can clear the DTCs

Diagnostic Aids
- Check and correct any abnormal engine noise before using the diagnostic table.
- Thoroughly check any suspected circuity for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks Improperly formed connectors
- Damaged terminals
- Poor terminal to wiring connections
- Physical damage to the wiring harness

Steps 1 - 4:

Steps 5 - 9:

Steps 10 - 12:

Test Description
The number(s) below refer(s) to the step number(s) 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 suspected circuitry for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal to wiring connections
- Physical damage to the wiring harness
7. Reprogram 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 and the CKP System Variation Learn Procedure for the crankshaft position system variation learn procedure.