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 P0327: Knock Sensor (KS) Circuit Low Voltage Bank 1
DTC P0328: Knock Sensor (KS) Circuit High Voltage Bank 1

### Circuit/System Description

The knock sensor (KS) is a piezoelectric device that produces an AC voltage of different amplitude and frequency depending on the level of engine mechanical vibration. The KS system monitors the knock sensor in order to determine if detonation or spark knock is present. If the KS system determines that excessive knock is present, the engine control module (ECM) retards the spark timing based on the signal from the KS system. The KS produces an AC signal when specific frequencies are detected. The ECM then retards the timing until knock is controlled.

In order to differentiate between normal engine noise and spark knock, the ECM samples the KS signal. The ECM samples the KS signal for a certain length of time under different engine speeds and loads during non-cylinder knock events. This sampling is used to determine a range of acceptable normal engine noise.

### Conditions for Running the DTCs

• | The engine is running.

• | DTCs P0327 and P0328 run continuously once the above condition is met.

### Conditions for Setting the DTCs

#### P0327

The ECM detects a KS signal voltage that is less than the typical engine noise level.

#### P0328

The ECM detects the KS signal voltage is greater than the maximum normal engine noise level.

### Action Taken When the DTC Sets

DTCs P0327 and P0328 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0327 and P0328 are Type B DTCs.

### Diagnostic Aids

• | 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.

### 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 P0327 and P0328 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

1. Ignition OFF, and the MAIN fuse removed, disconnect the harness connector at the KS.
2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal 2 and ground.

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

3. Ignition ON, connect a test lamp between the signal circuit terminal 1 and ground.

⇒ | If the test lamp illuminates, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install the MAIN fuse. Ignition ON, connect a test lamp between the signal circuit terminal 1 and 12 volts.

⇒ | If the test lamp illuminates, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

5. 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