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Home >> Volvo >> 1995 >> 850 Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Turbo >> Diagnostic Trouble Code Testing >> MOTRONIC 4.3 Control System >> Code 1-4-3, 4-3-3: Front Knock Sensor Signal, Rear Knock Sensor Signal
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Code 1-4-3, 4-3-3: Front Knock Sensor Signal, Rear Knock Sensor Signal

  1. If fault is intermittent, check camshaft setting. See the 2.3L article in the ENGINES section. If camshaft setting is okay, check all wiring and connectors for poor contact. If fault is permanent, go to next step.
  2. Turn ignition off. Check camshaft setting in relation to crankshaft. Repair as necessary. If camshaft setting is okay, gain access to knock sensor(s) by removing upper charge air cooler pipe and engine cooling fan. To gain access to rear knock sensor also remove intake manifold support bracket.
  3. Ensure ignition is still off. Wait 2 minutes. Disconnect knock sensor. Connect an ohmmeter between knock sensor connector terminal No. 2 and ground. If ohmmeter reads about zero ohms, go to step 5). If ohmmeter does not read about zero ohms, go to next step.
  4. Ensure ignition is still off and knock sensor is disconnected. Ensure ECM connector is making good electrical contact and is connected securely to ECM. Connect an ohmmeter between knock sensor connector terminal No. 2 and ground. If ohmmeter reads about zero ohms, code was caused by poor contact in ECM connector. If ohmmeter does not read about zero ohms, check wiring between knock sensor connector terminal No. 2 and ECM connector terminal A17 for an open circuit.
  5. Ensure ignition is still off and knock sensor is disconnected. Connect an ohmmeter between knock sensor connector terminal No. 1 and ground. If ohmmeter reads about zero ohms, check wiring between knock sensor connector terminal No. 1 and ECM connector terminal A2 (Code 1-4-3) or terminal A30 (4-3-3) for short to ground. If ohmmeter reads about one megohm, go to step 7). If ohmmeter reads infinite resistance, go to next step.
  6. Ensure ignition is still off and knock sensor is disconnected. Ensure ECM connector terminals are free of resistance and oxidation. Reconnect ECM. Connect an ohmmeter between knock sensor connector terminal No. 1 and ground. If ohmmeter reads about one megohm, code is caused by poor contact in ECM's connector. If ohmmeter does not read about one megohm, check wiring between knock sensor connector terminal No. 1 and ECM terminal A2 (Code 1-4-3) or terminal A30 (Code 4-3-3) for an open circuit.
  7. Reconnect knock sensor(s). Start and warm up engine. Increase engine speed to slightly greater than 3500 RPM. Use Volvo Scan Tool (998-8686 ) to check knock sensor value. If knock sensor value is 2-6 at speeds greater than 3500 RPM, source of code is poor contact at knock sensor connector. If knock sensor value is not 2-6 at speeds greater than 3500 RPM, test system using a new knock sensor.
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