P0325

Code P0325, Knock Sensor Circuit:

Knock Sensor Circuit Schematic:

CIRCUIT DESCRIPTION
The knock sensor is used to detect engine detonation and allow the PCM to retard the Ignition Control (IC) timing based on the signal being received. The circuitry within the knock sensor causes the PCM's supplied 5 volts signal to be pulled down, so that under a no knock condition CKT 496 would measure about 2.5 volts. The knock sensor produces an AC signal which rides on the 2.5 volts DC voltage. The amplitude and signal frequency is dependent upon the knock level.

If CKT 496 becomes open or shorted to ground, the voltage will either go above 3.5 volts or below 1.5 volts. If either of these conditions are met for 20 seconds, DTC P0325 will be stored.

DTC P0325 WILL SET WHEN:
^ Voltage on CKT 496 goes above 3.6 volts or below 1.5 volts.
^ Either condition present for 20 seconds.

ACTION TAKEN (PCM will default to):
With DTC P0325 set, the PCM will illuminate the MIL (Service Engine Soon) for the remainder of the key cycle and retard spark timing ("Knock Retard") by 10 degrees.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If DTC P0325 is detected, the PCM will retard spark timing by 10 degrees. If an audible knock is heard from the engine, repair the internal engine problem; normally no knock should be detected at idle.
2. The PCM applies 5 volts through a pull-up resistor which should be present at the knock sensor terminal.
3. This test determines if the knock sensor is faulty or if the knock sensor portion of the PROM is faulty.

DIAGNOSTIC AIDS
^ Check CKT 496 for a intermittent open or short to ground. Also check for proper installation of PROM.
^ If the knock sensor CKT 496 is routed too close to secondary ignition wires it may induce a voltage and cause a false knock signal.
^ Refer to "DIAGNOSIS BY SYMPTOM/DETONATION, SPARK KNOCK," Detonation/Spark Knock/Pings