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    2007 Pontiac Grand Prix 3.8L SFI OHV 6cyl

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    Knock Sensor

    Inspect/Test/Replace

    Most computer-controlled systems use knock sensors to retard timing when the engine is experiencing pinging or knocking.

    A knock (detonation) sensor.

    Obviously, a faulty knock sensor produces problems that appear to be ignition-system-related. If the knock sensor system does not provide an engine detonation signal to the PCM (powertrain control module), the engine detonates, especially on acceleration.

    • The first step in diagnosing the knock sensor and knock sensor module is to check all the wires and connections in the system for loose connections, corroded terminals, and damage.
    • With the ignition switch on, be sure that 12 volts are being supplied through the fuse to the knock sensor module.
    • A quick check of a knock sensor is to watch the ignition's timing while the engine is running and the engine block is tapped with a hammer.
      • The noise should cause a change in timing.
    • The knock sensor can also be checked by tapping near the sensor and watching for an AC pulse on a DMM or lab scope.

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