Home » GM 6.5 » GM/Detroit 6.5L – Engine Management – FUEL CONTROL – INTAKE AIR TEMPERATURE (IAT) SENSOR


The Intake Air Temperature (IAT) sensor is mounted in the intake manifold (figure 5-25). Like the ECT sensor, the IAT is a thermistor that changes value based on temperature.
IAT resistance values are approximately the same as for the ECT sensor and are given below.

IAT Sensor Circuit Operation
The Intake Air Temperature (IAT) sensor receives a 5 volt signal from the PCM on CKT 472 (figure 5-26). IAT sensor resistance changes inversely according to temperature. Low intake air temperatures cause high sensor resistance, which results in higher voltage as seen by the PCM. High intake air temperatures cause low resistance and low voltage. Circuit voltage ranges from almost 5 volts at low temperatures to less than 1 volt at high temperatures.

The PCM uses the IAT sensor signal to adjust fuel delivery according to incoming air temperature.

The IAT sensor shares a common ground with the ECT sensor, crankshaft position sensor, and boost sensor on CKT 452.

DTC 47 — “Intake Air Temperature (IAT) Circuit Low (High Temperature Indicated)”
DTC 47 sets when engine coolant temperature is below 38°C (100°F) and intake air temperature is above 96°C (205°F) for 2 seconds of more. This would cause voltage on the circuit to be lower than normal.

DTC 48 — “Intake Air Temperature (IAT) Circuit High (Low Temperature Indicated)”
DTC 48 sets when intake air temperature falls below -38°C (-39°F) for 2 minutes. This causes a higher-than-normal voltage signal on the circuit back to the PCM.


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