Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSAAB1994900 SE, 4D HATCHBACK, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTSIGNITION SYSTEMTIMING CONTROL SYSTEMSKNOCK SENSOR
1994 Saab 900 SE, 4D Hatchback, Automatic
Knock Sensor
1994 Saab 900 SE, 4D Hatchback, AutomaticSECTION Knock Sensor
- 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.
- 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.
- 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).
- 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.
- Inspect shield for continuity between sensor harness connector and ignition ECM pin No. 30. Inspect shield for short to ground. Replace wire if defective.
- 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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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.