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DTC P0071: Ambient Temp Sensor Performance: Testing

NOTE: If DTC P1192 or P1193 is also set, diagnose those DTCs first. See DTC P1192: INLET AIR TEMP SENSOR VOLTAGE LOW  or DTC P1193: INLET AIR TEMP SENSOR VOLTAGE HIGH  .
  1. Turn the ignition on. With the DRBIII(R), read DTCs. Is the Good Trip counter displayed and equal to zero? If yes, go to next step. If no, go to step  7 .
  2. Turn the ignition off. Disconnect the IAT sensor harness connector. Turn the ignition on. With the DRBIII(R), read the IAT voltage. Is the voltage more than 4.6 volts? If yes, go to next step. If no, go to step  4 .
  3. Turn the ignition off. Using a jumper wire, jumper across the IAT sensor harness connector terminals. Turn the ignition on. With the DRBIII(R), read the IAT voltage. Is the voltage less than one volt? If yes, replace the IAT sensor. If no, go to next step.
    4. NOTE: Ensure the voltmeter leads meet the terminals in the connector and that there is good terminal-to-wire connection. Ensure the voltmeter leads are connected for positive polarity.
  4. Turn the ignition off. Remove jumper wire. Reconnect IAT sensor harness connector. Perform a voltage drop test by backprobing between the sensor ground circuit in the IAT sensor harness connector and PCM harness connector. Start the engine. Allow the engine to idle. Is the voltage less than 0.10 volt? If yes, go to next step. If no, repair high resistance in sensor ground circuit.
    5. NOTE: Ensure the voltmeter leads meet the terminals in the connector and that there is good terminal-to-wire connection. Ensure the voltmeter leads are connected for positive polarity.
  5. Turn the ignition off. Perform a voltage drop test by backprobing between the IAT sensor signal circuit in the IAT sensor harness connector and PCM harness connector. Start the engine. Allow the engine to idle. Is the voltage less than 0.10 volt? If yes, go to next step. If no, repair high resistance in IAT sensor signal circuit.
  6. There are no possible causes remaining, replace PCM.
    7. WARNING: When the engine is operating, DO NOT stand in a direct line with the fan. DO NOT put your hands near the pulleys, belts or fan. DO NOT wear loose clothing.
  7. Conditions that set DTC are not present at this time. The following list may help in identifying the intermittent condition:
    • With the engine running at normal operating temperature, monitor the DRBIII(R) parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set.
    • Review the DRBIII(R) Freeze Frame information to identify under what conditions the DTC set.
    • Refer to any Technical Service Bulletin (TSB) that may apply.
    • Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
    • Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

    Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.

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