P037

Code PO37:

Sensor Circuit:

DESCRIPTION:
The Intake Air Temperature (IAT) sensor is a thermistor, or variable resistor, that varies resistance based on temperature. As the temperature of the sensor increases, resistance decreases. High temperature will result in low signal voltage. Code P037 sets when the PCM sees a IAT sensor reading of 148°C when the coolant is less than 100°C.

TEST CONDITIONS:
1. Codes P014 and P015 not set.

2. Engine coolant temperature 100°C or less.

FAILURE CONDITIONS:
IAT 148°C or greater.

ACTION TAKEN:
1. PCM turns 'ON' the 'SERVICE ENGINE SOON' MIL.

2. PCM substitutes 40°C for IAT when engine coolant temperature is 40°C or greater.

3. PCM substitutes engine coolant temperature for IAT when engine coolant temperature is less than 40°C.

NOTES ON FAULT TREE:
1. If the IAT sensor is shorted, PCM Data PD05 should read 148°C or greater. If it does not, then the sensor is not shorted, see 'NOTE ON INTERMITTENTS'.

2. Checking for sensor shorted or CKT 472 shorted to ground. If PCM Data PD05 stays at 148 - 151°C with the sensor unplugged, then CKT 472 is shorted to ground.

3. IAT sensors can be damaged by a 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.

4. Fault is most likely at PCM connector or PCM. Before PCM is replaced, check for damaged pins or poor connection.

NOTES ON INTERMITTENTS:
Manipulate CKT 472 wiring, the IAT sensor connector and the PCM connector while observing PCM Data PD05. If the failure is induced, the manifold air temperature will jump from its normal value to the shorted reading 148°C - 151°C. Remove and reinstall both the IAT and PCM connectors and ensure that they are latched. If wiring and connectors check out OK, substitute a known good IAT sensor and retest.