Join Date: Aug 2019
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Ignition ON, if the engine is cold, a properly functioning IAT sensor will gradually increase the scan tool IAT Sensor parameter. This is due to the heat that is generated by the mass air flow (MAF) sensor heating elements.Circuit/System Verification
Depending on the ambient temperature, an IAT sensor signal circuit or low reference circuit that is shorted to the MAF sensor signal circuit can cause a DTC P0113 to set. This condition causes a rapid fluctuation in the IAT Sensor parameter.
An IAT sensor signal circuit that is shorted to the MAF sensor ignition circuit can cause a DTC P0113 to set.
If the ignition has been OFF for 8 hours or greater , the IAT and the ECT should be within 15°C (27°F) of each other and also the ambient temperature. Ignition ON, observe the scan tool Start-up ECT and Start-up IAT Sensor parameters. Compare those sensor parameters to each other and also to the ambient temperature to determine if the IAT sensor is within an acceptable operating range.Circuit/System Testing
Engine running, observe the scan tool IAT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current ambient temperature and the vehicle operating conditions.
Ignition OFF, disconnect the harness connector at the IAT sensor.Component Testing
Ignition OFF for 90 seconds , test for less than 5 ohm of resistance between the low reference circuit terminal E and ground.
¤ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the engine control module (ECM).
Ignition ON, verify the scan tool IAT parameter is less than -39°C (-38°F) .
¤ If greater than the specified range, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the ECM.
Install a 3A fused jumper wire between the signal circuit terminal D and a good ground. Verify the scan tool IAT parameter is greater than 149°C (300°F) .
¤ If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, test or replace the IAT sensor.
Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature Vs Resistance table.
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