Knock Sensor (KS)

1995 Saab 900 SE, 4D Hatchback, AutomaticSECTION Knock Sensor (KS)
  1. 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 and go to next step.
  2. Locate knock sensor under intake manifold. Unplug connectors from sensor and ignition ECM. Inspect wiring between knock sensor and ECM connector. See the WIRING DIAGRAMS - 2.5L V6 article. If open or short circuit is located, repair as necessary. Reconnect knock sensor and ECM, and retest system. If wiring is good, go to next step.
  3. Temporarily replace knock sensor with known good unit. Repeat step 1). If timing still does not retard, reinstall original sensor and replace ECM.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.