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DTC P0031: O2 Sensor 1/1 Heater Circuit Low & P0037: O2 Sensor 1/2 Heater Circuit Low: Testing

  1. With the ignition on, but the engine not running. With the DRBIII® scan tool, read DTCs and record the related freeze frame data. Is the Good Trip Counter displayed and equal to zero? If yes, go to step  3. If no, go to next step.
  2. Turn the ignition off. Allow the O2 sensor to cool down before continuing the test. The O2 sensor voltage should stabilize at 5.0 volts. Raising the hood may help in reducing under hood temperatures quicker. Ignition on, engine not running. With the DRBIII® scan tool, actuate the O2 heater test. With the DRBIII® scan tool, monitor O2 sensor voltage for at least 2 minutes. Does the O2 sensor voltage stay above 4.5 volts? If yes, go on to the next step. If no, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
  3. Turn the ignition off. Allow the O2 sensor to cool down to room temperature. Disconnect the O2 sensor harness connector. Measure the resistance across the O2 sensor heater element component side. Heater resistance specification, 3.0-4.0 ohms (1/1 and 1/2) or 4.0-5.0 ohms (1/2 and 2/2). Is the O2 sensor heater element within specification? If yes, go to next step. If no, replace the O2 sensor.
  4. Turn the ignition off. Disconnect the O2 sensor harness connector. Ignition on, engine not running. With the DRBIII® scan tool, actuate the O2 heater test. Using a 12-volt test light connected to ground, probe the O2 heater control circuit in the O2 sensor harness connector. Does the test illuminate brightly and flash on and off? If yes, replace the O2 sensor. If no, go to next step.
    5. NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
  5. Turn the ignition off. Disconnect the O2 sensor harness connector. Disconnect the PCM harness connectors. Measure the resistance between ground and the O2 heater control circuit in the O2 sensor harness connector. Is the resistance below 5.0 ohms? If yes, repair the short to ground in the O2 sensor heater control circuit. If no, replace and program the PCM. See PROGRAMMING .
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