For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0325: Knock Sensor (KS) 1 Circuit
DTC P0326: Knock Sensor (KS) 1 Performance
DTC P0330: Knock Sensor (KS) 2 Circuit
DTC P0331: Knock Sensor (KS) 2 Performance

### Circuit/System Description

The knock sensor (KS) enables the engine control module (ECM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The ECM adjusts the spark timing based on the amplitude and the frequency of the KS signal. The ECM receives the KS signal through a signal circuit. The ECM supples a ground circuit to the KS through a low reference circuit. The ECM also supplies a shielded ground circuit to the KS. The ECM learns a KS noise level at idle and uses calibrated values for the rest of the engine speed range. The ECM should monitor a normal KS signal within the noise channel. The circuits between the KS sensor and the ECM consist of the following circuits:

• | A KS signal

• | A low reference

• | A shielded ground

### Conditions for Running the DTC

• | DTCs P0016, P0335, P0336, and P0340 are not set.

• | The engine coolant temperature (ECT) is greater than 65°C (149°F).

• | The engine speed is greater than 2,496 RPM--P0325 and P0330

• | The mass air flow (MAF) is greater than 251 mg/stk.

• | The DTCs run continuously once the above conditions are met.

### Conditions for Setting the DTC

The ECM detects an incorrect KS signal.

### Action Taken When the DTC Sets

DTC P0325, P0326, P0330, and P0331 are Type B DTCs.

### Conditions for Clearing the DTC

DTC P0325, P0326, P0330, and P0331 are Type B DTCs.

### Diagnostic Aids

The following conditions could also set this DTC:

• | Inspect the KS for physical damage. A KS that is dropped or damaged may cause a DTC to set.

• | Inspect the KS for proper installation. A KS that is loose or over torqued may cause a DTC to set. The KS should be free of thread sealant. The KS mounting surface should be free of burrs, casting flash, and foreign material.

• | The KS must be clear of hoses, brackets, and engine electrical wiring.

• | An electromagnetic interference (EMI) condition on the shielded ground circuit

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Knock Sensor (KS) System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Engine running, observe the DTC information with a scan tool. DTCs P0325, P0326, P0330, or P0331 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

Important: If the KS lead is damaged in any way, replace the KS.

1. Ignition OFF, disconnect the harness connector at the appropriate KS.
2. Ignition ON, test for less than 1.5 volts between the signal circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

3. Test for less than 1.5 volts between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Ignition OFF, test for 96K-107K ohms of resistance between the signal circuit terminal 1 and ground.
5. If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒ | If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

6. Test for 96K-107K ohms of resistance between the signal circuit terminal 1 and low reference circuit terminal 2.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

7. If all circuits test normal, test or replace the KS sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Knock Sensor Replacement

• | Control Module References for engine control module replacement, setup, and programming