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Home › Volvo › 1997 › V90 AW30-40 › Repair and Diagnosis › Engine Performance › System › Engine Controls - Tests W/Codes › Diagnostic Tests › DTC 143 Or 433: Knock Sensor Signal

DTC 143 Or 433: Knock Sensor Signal

  1. If fault is permanent, go to next step. If fault is intermittent, turn ignition off. Wait 2 minutes. Disconnect knock sensor(s). Connect ohmmeter between knock sensor connector terminal No. 1 and ground. If ohmmeter reads about one megohm, system is okay. If ohmmeter does not read about one megohm, check wiring between knock sensor terminal No. 1 and ECM connector terminal A2 (DTC 143) or terminal A30 (DTC 433) for a short to ground.
  2. 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 4). If ohmmeter does not read about zero ohms, go to next step.
  3. 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, DTC 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.
  4. 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 (DTC 143) or terminal A30 (DTC 433) for short to ground. If ohmmeter reads about one megohm, go to step 6). If ohmmeter reads infinite resistance, go to next step.
  5. 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, DTC is caused by poor contact at ECM connector. If ohmmeter does not read about one megohm, check for open circuit in wiring between knock sensor connector terminal No. 1 and ECM connector terminal A2 (DTC 143) or terminal A30 (DTC 433).
  6. Reconnect knock sensor(s). Start and warm up engine. Increase engine speed to 3500 RPM. Use Volvo Scan Tool (998-8686 ) to check knock sensor value (scrolling values list). If knock sensor value is 2-6 at speeds greater than 3500 RPM, source of DTC 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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