Diagnostic Aids

Check wiring harness routing for a potential short circuit to ground in IAT signal circuit. Scan tester displays intake air temperature in degrees centigrade. A faulty connection or an open in IAT signal circuit or sensor ground circuit will cause DTC 48 to set. Test intake air temperature sensor at various temperature levels to evaluate possibility of a skewed (mis-scaled) sensor. See TEMPERATURE VS. RESISTANCE VALUES table. A skewed sensor could result in poor driveability complaints.

Fig 1: DTC 48 Schematic ("G" Series) IAT Sensor Circuit High (Low Temperature Indicated)

Fig 2: DTC 48 Schematic ("P" Series) IAT Sensor Circuit High (Low Temperature Indicated)

Fig 3: DTC 48 Flow Chart (All Models) IAT Sensor Circuit High (Low Temperature Indicated)