For 1990-2009 cars
Engine Controls Components
Cell 20: MAF, IAC, Knock Sensors
OBD II Symbol Description Notice

### Circuit Description

The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. Input signals from the knock sensors are used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the amplitude and frequency of the KS signal being received. The knock sensors produce an AC signal under all engine operating conditions. During engine operation, the PCM calculates the average voltage of each knock sensor's signal. If the knock sensor system is operating normally, the PCM should monitor KS signal voltages varying from 0.1 to 1.0 volt. If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuits, DTC P0325 will set.

### Conditions for Running the DTC

• | No TP sensor , VSS, CKP, MAF, or ECT, DTCs set.

• | Engine Speed is between 1000 and 4000 RPM.

• | Throttle angle is greater than 15%.

• | Engine load is greater than 45%.

• | Engine coolant temperature is greater than 75°C (167°F).

• | Maximum spark retard is less than 15.

• | System voltage is greater than 9 volts

### Conditions For Setting the DTC

• | The PCM detects a malfunction in the intergrated knock sensor diagnostic circuitry which will not allow proper diagnosis of the knock sensor circuits.

• | Above condition for at least 1 second.

### Action Taken When the DTC Sets

• | The PCM will not illuminate the Malfunction Indicator Lamp (MIL).

• | The PCM will store conditions which were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data.

• | The PCM will use a calculated spark retard value to minimize knock during conditions when knock is likely to occur. The calculated value will vary based on engine speed and load.

### Conditions for Clearing the MIL/DTC

• | A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using the scan tool Clear Info function.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. Ensures that the malfunction is present.

2. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

#### DTC P0325 - KS System

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 | Important:: If an engine knock can be heard repair the engine mechanical problem before proceeding with this diagnostic. Refer to Engine Noise Diagnosis in Engine Mechanical.

1. Operate engine within conditions specified in diagnostic support. Refer to Conditions for Setting the DTC.
2. Using a scan tool, monitor Specific DTC info for DTC P0325 until the DTC P0325 test runs.

Note test result; does scan tool indicate DTC P0325 failed this ign?

--

Go to Step 4

Go to Step 3

3 |

1. Turn ON the ignition switch.
2. Review and record scan tool Fail Records data for DTC P0325.
3. Operate vehicle within Fail Records conditions.
4. Using a scan tool, monitor Specific DTC info for DTC P0325 until the DTC P0325 test runs.

Does scan tool indicate DTC P0325 test failed this ign?

--

Go to Step 4

Go to Diagnostic Aids

4 | Replace the PCM. Important:: The replacement PCM must be programmed. Go to Powertrain Control Module Replacement/Programming Is action complete? | -- | Go to Step 5 | --
5 |

1. Review and record Fail Records data
2. Clear DTCs.
3. Operate the vehicle within Fail Records conditions.
4. Using a scan tool, monitor Specific DTC info for DTC P0325 until the DTC P0325 test runs.

Does the scan tool indicate DTC P0325 test failed this ign?

--

Go to Step 2

System OK