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Home >> Acura >> 1991 >> Legend Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 23: Left Knock Sensor
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Code 23: Left Knock Sensor

NOTE: For wiring diagrams, see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. For vacuum diagrams, see VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section.
NOTE: Repair any engine knocking sounds before performing this test.
  1. Turn ignition off. Remove ACG fuse in underdash fuse box for 10 seconds to reset ECU. Warm engine until cooling fan comes on. With transmission in Neutral, hold engine speed at 3000-4000 RPM for 10 seconds.
  2. Check if CHECK ENGINE light flashes Code 23. If light does not flash Code 23, problem is intermittent. Check for poor connections and loose wires at knock sensor connector, ECU and terminals in connector C353 at right shock tower.
  3. If CHECK ENGINE light flashes Code 23, turn ignition off. Connect ECU test harness to harness connector only (not ECU). See Figure . Disconnect knock sensor connector.
  4. Check for continuity between D4 and ground. If no continuity exists, go to next step. If continuity is present, repair short in Red/Blue wire between D4 terminal at ECU and knock sensor.
  5. Check for continuity between ECU terminal D4 and Red/Blue wire at knock sensor connector. If continuity is present, go to next step. If no continuity exists, repair open in Red/Blue wire between D4 terminal at ECU and knock sensor.
  6. If continuity is present, replace knock sensor with a known good one. Retest vehicle for code. If condition goes away, replace knock sensor. If condition is still present, replace ECU.
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