Diagnostic Aids

Check wiring harness routing for a potential short circuit to ground. After starting engine, coolant temperature should rise to about 185°F (85°C). PCM default value will flash on data screen intermittently.

Test engine coolant 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 15 Schematic ("G" Series) ECT Sensor Circuit High (Low Temperature Indicated)

Fig 2: DTC 15 Schematic ("P" Series) ECT Sensor Circuit High (Low Temperature Indicated)

Fig 3: DTC 15 Flow Chart (All Models) ECT Sensor Circuit High (Low Temperature Indicated)