Roadmaster 1992

Knock Sensor



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Fig. Knock sensor location-1991-1993


The Knock Sensor (KS) is a piezo-electric (pressure-sensitive) electronic device that enables the Powertrain Control Module (PSM) to control the ignition timing for optimum performance, and to protect the engine from potentially damaging levels of detonation. The PCM uses the KS system to test for abnormal engine noise that may indicate detonation, which is also known as spark knock.

Removal & Installation

  1. Before servicing the vehicle, refer to the Precautions Section.
    Disconnecting the negative battery cable on some vehicles may interfere with the functions of the on-board computer systems and may require the computer to undergo a relearning process, once the negative battery cable is reconnected.

    If working near and/or around the SRS system and components, be sure to properly disable the SRS system. See disarming/arming the SRS system.

  3. Disconnect the negative battery cable.
  5. Raise and safely support the vehicle.
  7. Disconnect the electrical connector.
  9. Remove the sensor from its mounting.

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    Fig. Knock sensor and related components-1991-1993


To install:

Be sure to use new fasteners, as required.

Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread sealer are identified. Do not use paints, lubricants or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners.

  1. Installation is the reverse of the removal procedure.
  3. Using the GM diagnostic scan tool or aftermarket equivalent reprogram the necessary systems and components. Be sure to follow the scan tool manufacturer-s directions.


Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.

Knock Sensor Strategy

The Knock Sensor (KS) system uses one or two broadband one-wire sensors. The Knock Sensor generates an AC voltage signal of varying amplitude and frequency based on the engine vibration. The amplitude and frequency are dependent upon the level of knock that the KS detects. The control module receives the KS signal through a signal circuit, and the KS ground is supplied by the engine block through the sensor housing.

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Fig. Active Knock Sensor (KS) Pattern

Related Diagnostic Trouble Codes

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Fig. Related Diagnostic Trouble Codes