P0325

DTC P0325 KS Module Circuit




Circuit Description
The knock sensor is used to detect engine detonation, allowing the powertrain control module (PCM) to retard ignition control (IC) spark timing based on the knock sensor (KS) signal being received. The knock sensor produces an AC signal so that under a no knock condition the signal on the KS circuit measures about 0.007 V AC. The KS signal's amplitude and frequency depend upon the amount of knock being experienced. The PCM contains a non-replaceable knock filter module called a signal-to-noise enhancement filter (SNEF) module. This filter module in the PCM determines whether knock is occurring by comparing the signal level on the KS circuit with the voltage level on the noise channel. The noise channel allows the PCM to reject any false knock signal by knowing the amount of normal engine mechanical noise present. Normal engine noise varies depending on engine speed and load. When the PCM determines that an abnormally low noise channel voltage level is being experienced, a DTC P0325 will set.

Conditions for Setting the DTC
- Engine has been running for at least 30 seconds.
- The PCM determines that its internal signal from its knock filter module indicates a continuous knocking condition for more than 10 seconds.

Action Taken When the DTC Sets
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.
- The PCM will use a substitute default spark retard value of 6 degrees to minimize knock during conditions when knock is likely to occur.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0325 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- DTC P0325 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 PCM - Inspect the knock sensor 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 circuits such as spark plug coils.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Steps 1 - 4:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
2. Ensures that the fault is present.