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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 1-2-3: Engine Coolant Temperature Sensor Signal

Code 1-2-3: Engine Coolant Temperature Sensor Signal

  1. If ECM receives a signal from ECT sensor which indicates a temperature less than -49°F (-45°C), or greater than 300°F (150°C), this is interpreted as a fault and DTC 1-2-3 is set.
  2. If Codes 3-1-4, 4-1-1, and/or 4-1-3 are set, check ECT sensor, CMP sensor, TP sensor, and EGR temperature sensor joint connector terminal A18 on ECM for signs of contact resistance and/or oxidation. If no other codes are stored, go to next step.
  3. If fault is permanent, go to next step. If fault is intermittent and signal is too high, check all connectors for an intermittent open or short circuit to voltage. If fault is intermittent and signal is too low, check wiring between ECT sensor connector terminal No. 1 and ECM terminal A31 for an intermittent short to ground.
  4. If fault is permanent and signal is too low, go to step 10). If fault is permanent and signal is too high, turn ignition off. Wait 90 seconds, then disconnect ECT sensor. Connect an ohmmeter between ECT sensor connector No. 2 and ground.
    NOTE: Fan run-on must be allowed to finish before taking resistance measurements.
  5. If ohmmeter shows about zero ohms, go to next step. If ohmmeter does not show about zero ohms, go to step 7).
  6. Turn ignition on. Disconnect ECT sensor connector. Connect voltmeter between ECT sensor connector terminal No. 1 and 2. If voltmeter shows about 5 volts, go to step 8). If voltmeter shows about zero volts, go to step 9). If voltmeter shows more than about 5 volts, check wiring between ECT sensor connector terminal No. 1 and ECM terminal A31 for a short to voltage, then check resistance between ECT sensor terminals. Ohmmeter should show about 2200 ohms. If resistance is incorrect, retest using a known good ECT sensor.
  7. Ensure ignition is off. Disconnect ECT sensor connector. Check ECM connector for poor contact and/or oxidation. Reconnect ECM connector. Connect an ohmmeter between ECT sensor connector terminal No. 2 and ground. If ohmmeter shows about zero ohms, code is caused by poor contact in ECM connector. If ohmmeter does not show about zero ohms, check wiring between ECT sensor connector terminal No. 2 and ECM terminal A18 for an open circuit.
  8. Ensure ignition is off. Disconnect ECT sensor connector. Connect an ohmmeter between ECT sensor connector terminals No. 1 and 2. If ohmmeter does not show about 2200 ohms, repeat test using a known good ECT sensor. If ohmmeter does show about 2200 ohms, check for poor contact at ECT sensor connector.
  9. Ensure ignition is off. Disconnect ECT sensor connector. Ensure ECM connector has good terminal contact. Reconnect ECM connector. Turn ignition on. Connect voltmeter between ECT sensor connector terminals No. 1 and 2. If voltmeter shows about 5 volts, check for poor contact at ECM connector. If voltmeter does not show about 5 volts, check wiring between ECT sensor connector terminal No. 1 and ECM connector terminal A31 for an open circuit.
  10. If fault is permanent and signal is too low, turn ignition off. Disconnect ECT sensor. Turn ignition on. Connect voltmeter between ECT sensor connector terminal No. 1 and ground. If voltmeter shows about 5 volts, retest system using a known good ECT sensor. If voltmeter does not show about 5 volts, check wiring between ECT sensor terminal No. 1 and ECM connector terminal A31 for a short to ground.
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