Diagnostic Aids

After engine is started, temperature should rise steadily to about 203°F (95°C) and then level off when thermostat opens.

Ensure engine is not overheating and has not been subjected to conditions which would create an overheating condition (i.e., overload, trailer towing, heavy stop and go traffic, etc.).

When replacing ECT sensor, check TEMPERATURE TO RESISTANCE VALUES table. A "shifted" sensor could result in poor driveability complaints.

Fig 1: Code 15 - Schematic Engine Coolant Temperature Sensor Circuit, High Temp. Indicated

Fig 2: Code 15 - Flow Chart Engine Coolant Temperature Sensor Circuit, High Temp. Indicated