P038

Circuit Description

The Intake Air Temperature (IAT) sensor is a thermistor, or variable resistor, that varies resistance based on temperature. Low temperature will result in a high signal voltage. Code P038 sets when the PCM sees a high resistance signal with outside air temperature -10°C or greater.

Test Condition(s)

1. Code P047 is not set.
2. Outside air temperature sensor has not failed.
3. Outside air temperature -10°C or greater, or the difference between outside air temperature and IAT is greater than 17°C.
4. Vehicle speed 7 mph or more for at least 5 seconds.
5. RPM 500 or more for 20 seconds.

Failure Condition(s)

IAT -37°C or less.

Action Taken

1. PCM turns 'ON' the 'SERVICE ENGINE SOON' MIL.
2. PCM substitutes outside air temperature for IAT.
3. Transaxle shift adapts are maintained at current levels.

Notes on Fault Tree

1. IAT sensor is open, PCM data PD05 should read -32°C or less. If it does not, then the sensor is not open.
2. Checking PCM and CKT 472 from PCM to connector C127. If PCM Data PDO5 reads 147°C-151°C with connector Pin A shorted to ground, then CKT 472 and PCM are OK.
3. Checking for an open sensor ground CKT 469. If PCM data PDO5 reads 147-151°C with connector pin A jumpered to pin 'B' then CKT 469 and PCM are OK.
4. Checking if CKT 472 or PCM is open.
5. Checking if CKT 472, CKT 469 or IAT sensor is open or shorted to voltage inside intake manifold.
6. IAT sensors can be damaged by backfire in the intake manifold. If the vehicle has had more than one IAT sensor replaced, check for signs of backfire or high intake manifold temperature due to improper valve train operation.