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Home >> Volkswagen >> 1988 >> Fox Base >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - BOSCH Cis-E >> Testing >> Electrical Components >> Knock Sensor (16-Valve Engines Only)
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Knock Sensor (16-Valve Engines Only)

  1. With ignition off, disconnect knock sensor from control unit. Measure resistance between terminals No. 13 and 14. Type I sensor should have 300 k/ohms. A Type II sensor should measure infinity (4). Reconnect sensor to control unit.
  2. Connect LED Test Light (US 1115) to single lead (Brown) connector and to battery (+) voltage. LED must light.
    CAUTION: Do not use a standard test light to test knock sensor. Higher voltage type light may damage control unit.
  3. With engine running, LED should go out (may glow slightly). Increase engine RPM one time to 3000 RPM. If LED lights again connect a jumper wire between outside terminals of knock sensor connector and momentarily (3 seconds) ground (-) center terminal.
  4. The LED light will blink on and off in a pattern. Blinking 2 times at intervals indicates a fault in the knock sensor (sensor defective, wiring, mounting torque) or defective control unit.
  5. If the LED light blinks 3 times in intervals it indicates a break in the vacuum hose to the control unit or the control unit vacuum sensor is defective.
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