Intake air temp circuit

DTC P0112 OR DTC P0113
Code Definition
†DTC P0112: Intake Air Temperature Sensor Circuit Low Input
†DTC P0113: Intake Air Temperature Sensor Circuit High Input

Circuit Description
The IAT sensor is built into MAP sensor. The MAP/IAT sensor is a variable resistor that changes resistance as intake air temperature changes. ECM uses MAP/IAT sensor signal to control fuel injector pulse width. When cold air is detected ECM will increase injector pulse width. When warm air is detected ECM will decrease injector pulse width.

Failure Conditions
ECM determines fault exists, sets DTC P0112 and turns the MIL when for 0.2 seconds during 2 drive cycles an air intake temperature of -49°F (45°C) is indicated by the MAP/IAT sensor. This check is made after at least 4 minutes and 10 seconds have passed since engine started and then idles for 30 seconds (with no fuel cut-off during a coast down). This code indicates a lower temperature is being read by the MAP/IAT sensor or ECM after the engine has been warmed up.

ECM determines fault exists, sets DTC P0113 and turns the MIL when for 0.2 seconds during 2 drive cycles an air intake temperature of 257°F (125°C) is indicated by the MAP/IAT sensor. This check is made after at least 4 minutes and 10 seconds have passed since engine started and then idles for 30 seconds (with no fuel cut-off during a coast down). This code indicates a higher temperature is being read by the MAP/IAT sensor or ECM after the engine has been warmed up.

Probable Cause
†Short to ground between ECM and IAT sensor.
†Open or short to voltage between ECM and IAT sensor.
†Short to each other in IAT circuits.
†Faulty IAT sensor.

Test Procedure
NOTE:
It is recommended that vehicle cool down overnight before starting
IAT sensor test procedure.

1. Turn ignition on. Using scan tool, verify DTC P0112 or DTC P0113 is set.

2. Ensure engine is cooled to ambient air temperature. Measure ambient air temperature. Turn ignition on. Using scan tool, read MAP/IAT sensor temperature. If MAP/IAT sensor temperature and ambient air temperature are not about the same, go to next step. If MAP/IAT sensor temperature and ambient air temperature are about the same, no problem is indicated at this time. Problem is intermittent or was repaired and DTCs were not cleared. Clear DTCs and ensure MAP/IAT sensor is operating properly.

3. Turn ignition off. Disconnect MAP/IAT 4-pin connector. Turn ignition on. Measure voltage between ground and MAP/IAT connector terminal No. 2 (Red wire). Voltage should be 4.5-5.0 volts. If zero volts exist, go to next step. If 4.5-5.0 volts exist, go to step 5.

4. Turn ignition off. Disconnect ECM 81-pin harness connector. See
Fig. 6. Measure resistance between ECM 81-pin harness connector terminal No. 44 and MAP/IAT sensor harness connector terminal No. 2 (Green wire). If resistance is one ohm or less, go to next step. If resistance is more than one ohm, repair open in wire between MAP/IAT sensor and ECM 81-pin harness connector terminal No. 44. When repairs are completed, clear DTCs and verify MAP/IAT operation.

5. Turn ignition off. Disconnect MAP/IAT connector and ECM 81-pin harness connector. Measure resistance between ECM 81-pin harness connector terminal No. 56 and MAP/IAT sensor harness connector terminal No. 3 (Gray wire). If resistance is more than one ohm, repair open between MAP/IAT harness connector terminal No. 3 (Gray wire) and ECM 81-pin harness connector terminal No. 56. If resistance is one ohm or less, ensure ECM connector terminals are clean and tight. If connector terminals are okay, replace MAP/IAT sensor with a known-good component. Clear DTCs and verify MAP/IAT sensor operation. If problem still exists, replace ECM. When repairs are completed, clear DTCs and verify MAP/IAT operation.