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

Knock Sensor Control Unit (16-Valve Engines Only)

  1. Ensure ignition coil and Hall Effect control module are okay. Remove connector from knock sensor and turn ignition on. Check for battery voltage between connector pins No. 3 and 5.
  2. Measure battery voltage between terminals No. 6 and 3. Open throttle valve, voltage should drop to zero volts. If voltage does not drop to zero check throttle idle switch.
  3. Measure voltage between terminals No. 8 and 3 while opening throttle. Battery voltage should be present at full throttle. If battery voltage is not present check full throttle switch.
  4. Remove harness connector from Hall Effect sender at distributor. Turn ignition on and measure voltage between outer terminals of connector. Voltage should be 5 volts minimum. Turn ignition off.
  5. With ignition on, check voltage between terminals No. 1 (-) and 15 (+) of ignition coil. Touch center terminal of connector from Hall Effect control module to ground. Voltage should increase briefly to 2 volts minimum. If it does not, replace knock sensor control unit.