Diagnostic Aids
WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
- Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor. Engine coolant that is leaking through the sensor will create a high resistance short to ground. This condition results in less voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a warmer ECT.
- This diagnostic runs in a specific range. Measure and record the resistance of the ECT sensor at various ambient temperatures greater than -8°C (+18°F), then compare those measurements to the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .
- An IAT sensor that is skewed colder at various ambient temperatures due to greater resistance than is normal will increase the range between these 2 sensors. Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .
- A slight to moderate resistance in the IAT sensor signal circuit or low reference circuit will increase the range between these 2 sensors. This conditions results in a greater voltage on the IAT sensor signal circuit, which is interpreted by the ECM as a colder IAT.