GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 Regal 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC P0325, P0326, P0327, or P0328

DTC P0325, P0326, P0327, or P0328 LTD without Turbocharger

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) Circuit

DTC P0326: Knock Sensor (KS) Performance

DTC P0327: Knock Sensor (KS) Circuit Low Voltage

DTC P0328: Knock Sensor (KS) Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

Knock Sensor Signal

P0327, P0328

P0325

P0325

P0327, P0328

P0326

Circuit/System Description

The knock sensor (KS) system 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 is located on the intake side of the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The ECM receives the KS signal through 2 isolated signal circuits. The ECM adjusts the spark timing based on the amplitude and the frequency of the KS signal.

Conditions for Running the DTC

P0325

This DTC runs continuously when:

    • The engine speed is greater than 1,500 RPM.
    • The engine coolant temperature (ECT) is greater than -40°C (-40°F).
    • The engine run time is greater than 1 second.
    • DTCs P0327 or P0328 are not set.

P0326

This DTC runs continuously when:

    • The engine speed is greater than or equal to 575 RPM.
    • The manifold absolute temperature (MAP) is greater than 10 kPa.
    • DTCs P0120, P0121, P0122, or P0123 are not set.

P0327, P0328

This DTC run continuously when:

    • The ECT is greater than -40°C (-40°F).
    • The engine run time is greater than 1 second.

Conditions for Setting the DTC

P0325

The KS signal circuits are open or shorted together for 6 seconds.

P0326

    • The KS signal indicates an excessive engine knock is present.
    • The ECM commanded spark retard at a given engine load and speed is more than the calibrated value.
    • The above conditions exist for 6 seconds.

P0327 and P0328

The KS signal circuits are shorted to ground or power.

Action Taken When the DTC Sets

DTC P0325, P0326, P0327, and P0328 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P0325, P0326, P0327, and P0328 are Type B DTCs.

Diagnostic Aids
    • Inspect the B68 KS for physical damage. A B68 KS that is dropped or damaged may cause a DTC to set.
    • Inspect the B68 KS for proper installation. A B68 KS that is loose or over torqued may cause a DTC to set. The B68 KS should be free of thread sealant.
    • The KS mounting surface should be free of burrs, casting flash, and foreign material.

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 Testing

P0325, P0327 and P0328

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

  1. Ignition ON, engine OFF.
  2. Disconnect the B68 KS harness connector.
  3. Measure for 2-5V between each of the following circuits and ground on the engine ECM side of the harness connector:
    4. • The B68 KS signal circuit, terminal A
    • The B68 KS signal circuit, terminal B
    ⇒If less than the specified range, test the circuits for a short to ground or an open/high resistance. If the circuits test normal, replace the K20 ECM.
    ⇒If greater than the specified range, test the circuits for a short to voltage. If the circuits test normal, replace the K20 ECM.
  4. If the circuits test normal, replace the KS.

P0326

       Note: If DTC P0327, P0328, P0335, P0336 are also set, diagnose those DTCs first.

    • Inspect for a loose or broken vehicle accessory or accessory bracket.
    • Inspect for excessive engine mechanical noise.

Component Testing
  1. Connect the DMM from the KS signal circuit terminal A to the KS signal circuit terminal B on the sensor side of the B68 KS harness connector.
  2. Set the DMM to the 400 mV AC hertz scale and wait for the DMM to stabilize at 0 Hz.

    3. Note: DO NOT tap on plastic engine components.

  3. Tap on the engine block with a non-metallic object near the B68 KS while observing the signal indicated on the DMM.
  4. The DMM should display a fluctuating frequency while tapping on the engine block.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Knock Sensor Replacement
    •  Symptoms - Engine Controls
    •  Symptoms - Engine Mechanical
    •  Control Module References for ECM replacement, setup, and programming