General fault in the intake air temperature (IAT) sensor circuit. IAT is typically integrated within the MAF on the 987.
SYMPTOMS
- Check-engine light
- Possible rough running
- Reduced performance
- Worse fuel economy
LIKELY CAUSES
- Faulty IAT sensor
- Open, shorted, or corroded wiring/connector
- Loss of reference voltage or ground
- ECM/PCM fault (rare)
DIAGNOSIS STEPS
- Inspect the IAT sensor connector and wiring for damage or corrosion
- Measure sensor resistance/voltage against specification
- Check reference voltage and ground at the connector
- Compare live data to a known-good value
- Replace the sensor if out of spec
RELATED PARTS
- IAT/MAF sensor