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Home >> GMC >> 1987 >> Forward Control 6.2 J, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 14 (Engine Controls - System/Component Tests - Gasoline) >> Engine Sensors & Switches >> Engine Controls - System/Component Tests - Gasoline >> Knock Sensor

Knock Sensor

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
  1. Disconnect knock sensor harness connector. Using an ohmmeter, measure knock sensor resistance between sensor terminal and engine block. Resistance should be 3300-4500 ohms. Connect voltmeter between sensor terminal and ground. Set voltmeter to 2-volt AC scale.
  2. Start and idle engine. Tap on engine block near sensor. A signal should be indicated on voltmeter. If no signal is indicated, replace knock sensor. Also see TIMING CONTROL SYSTEMS  under IGNITION SYSTEM and appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section below.
    • G - TESTS W/CODES - 4.3L
    • G - TESTS W/CODES - 5.0L
    • G - TESTS W/CODES - 5.7L
    • G - TESTS W/CODES - 7.4L
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