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Home >> Saab >> 1994 >> 900 Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Ignition System >> Timing Control Systems >> Knock Sensor
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Knock Sensor

  1. On vehicles with knock sensor, connect timing light. With engine running at a fast idle, tap cylinder head with a plastic mallet. If timing retards, knock sensor is okay. If timing does not retard, turn ignition switch off. Go to step 2) for 900 Series, or to step 4) for 9000 Series.
  2. On 900 Series, locate knock sensor under intake manifold. Unplug connectors from sensor and ignition ECM. Inspect Green wire for continuity between harness connector and ignition ECM pin No. 13. Also inspect Green wire for short to ground, to Brown wire, or to shield.
  3. Inspect Brown wire for continuity between harness connector and ignition ECM pin No. 12. Also inspect Brown wire for short to ground, to Green wire, or to shield. Ensure there is continuity between shield and ground. Replace wire assembly if defective. Go to step 6).
  4. On 9000 Series, locate knock sensor under intake manifold. Unplug connectors from sensor and ignition ECM. Inspect Gray wire for continuity between harness connector and ignition ECM pin No. 11. Also inspect Gray wire for short to shield or to ground.
  5. Inspect shield for continuity between sensor harness connector and ignition ECM pin No. 30. Inspect shield for short to ground. Replace wire if defective.
  6. Temporarily replace knock sensor with known good unit. Repeat step 1). If timing still does not retard, reinstall original sensor and replace ignition ECM.
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