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Home >> Jeep >> 2002 >> Liberty Limited, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0111: Intake Air Temp Sensor Performance >> Testing
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DTC P0111: Intake Air Temp Sensor Performance: Testing

  1. Turn ignition on, engine not running. With the DRBIII®, read DTCs. Is the Good Trip counter equal to zero? If yes, go to next step. If no, go to step  7.
  2. Turn the ignition off. Disconnect the Intake Air Temperature Sensor harness connector. Turn ignition on, engine not running. With the DRBIII®, read the IAT voltage. Is the voltage above 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. Turn ignition on, engine not running. With the DRBIII®, read the IAT voltage. Is the voltage below 1.0 volt? If yes, replace the Intake Air Temperature 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. Perform a voltage drop test of the Sensor ground circuit by backprobing the Sensor ground circuit at the IAT Sensor harness connector and PCM harness connector. Start the engine. Allow the engine to idle. Is the voltage below 0.10 volt? If yes, go to next step. If no, repair the high resistance in the Sensor ground circuit.
  5. Perform a voltage drop of the IAT Sensor Signal circuit, by backprobing the IAT Sensor harness connector and PCM harness connector. Start the engine. Allow the engine to idle. Is the voltage below 0.10 volt? If yes, go to next step. If no, repair the high resistance in the IAT Sensor Signal circuit.
  6. There are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .
    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. The conditions that set the DTC are not present at this time. The following may help in identifying the intermittent condition. With the engine running at normal operating temperature, monitor the DRBIII® 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® Freeze Frame information. If possible, try to duplicate the conditions under which the DTC was set. Refer to any Technical Service Bulletins (TSB) that may apply. With the DRBIII® as a Dual Channel Lab Scope and the Miller Special Tool (6801), backprobe the IAT Signal circuit at the Sensor connector and PCM connector. Start the engine and look for any differences in the two patterns. 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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