Circuit/System Testing

Always perform the Diagnostic System Check - Vehicle .

P0112 or P1112

1. Turn ON the ignition, with the engine OFF.
2. Disconnect the MAF/IAT sensor. Observe the IAT sensor with a scan tool for -36°C (-33°F).
   • If more than -36°C (-33°F), then test the signal circuit of the IAT sensor for a short to ground or a short to the IAT low reference circuit and repair as necessary. If all circuits test normal, replace the control module.
   • If less than -36°C (-33°F), replace the MAF/IAT sensor.
   • If IAT signal circuit tests OK, replace the control module.

P0113 or P1111

IMPORTANT: The sensor may be damaged if the circuit is shorted to a voltage source.
1. Turn ON the ignition, with the engine OFF.
2. Disconnect the MAF/IAT sensor.
3. Measure for 4.9-5.2 volts between the IAT sensor signal circuit and a good ground with a DMM.
   • If the voltage is less than 4.9 volts, test the IAT sensor signal circuit for high resistance or an open circuit.
   • If the voltage is more than 5.2 volts, test the IAT sensor signal circuit for a short to voltage, or any 5-volt reference.
   • If the IAT sensor signal circuit tests normal, and the voltage is still not within the proper range, then replace the control module.
4. Turn OFF the ignition, and all electrical accessories. Allow sufficient time for all of the control modules to power down before taking a resistance measurement.
5. Measure for less than 5 ohms of resistance between the IAT low reference circuit and a good ground.
   • If the resistance is more than 5 ohms, test the low reference circuit for high resistance or an open circuit. If the circuit tests normal, replace the control module.
   • If all circuits test normal, then replace the IAT sensor.