For 1990-2009 cars
Engine Controls Components
Ignition Control, Knock Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. The PCM uses the circuitry to diagnose the KS sensors and related wiring. The PCM calculates an average voltage of each knock sensor's signals and takes instantaneous signal voltage readings. The PCM uses the instantaneous signal voltage readings to determine the state of the knock sensor circuitry. If the knock sensor system is operating normally, the PCM should monitor instantaneous KS signal voltage readings varying outside a voltage range above and below the calculated average voltage. If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuit DTC 325 will set.

### Conditions for Running the DTC

1. No TP sensor, VSS, CKP sensor, CMP sensor, MAF sensor, or ECT sensor DTCs are set.
2. Engine speed:

- | Manual Transaxle - engine speed is between 1000 and 3000 RPM.

- | Automatic Transaxle - engine speed is between 1000 and 4000 RPM.

3. Throttle angle:

- | Manual Transaxle - Throttle angle is greater than 15%.

- | Automatic Transaxle - Throttle angle is greater than 3%.

4. Engine load:

- | Manual Transaxle - engine load is greater than 45%.

- | Automatic Transaxle - engine load is greater than 20%.

5. Engine coolant temperature is greater than 75°C (167°F).
6. Maximum spark retard is less than 15 degrees.
7. System voltage is greater than 9 volts.

### Conditions for Setting the DTC

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

• | The conditions are present for 300 3X reference periods (100 crankshaft revolutions).

### 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.

• | DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

### 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 - Knock Sensor Circuit

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