Fault in Engine Coolant Temperature Sensor Circuit
Indicates a problem with the engine coolant temperature sensor circuit.
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What it means (plain English)
The engine coolant temperature sensor measures how hot the coolant is and sends that information to the engine control module. If the sensor misbehaves, the engine may run inefficiently or overheat if ignored.
What the computer is actually seeing
The control module is seeing a voltage that is outside the expected range from the coolant temperature sensor, which typically ranges from 0.5V (cold) to 4.5V (hot).
What a healthy reading looks like
Expected voltage from the ECT sensor should be between 0.5V and 4.5V corresponding to coolant temperatures of -40°F to 248°F.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect wiring and connectors at the coolant temperature sensor for damage or corrosion. Are they in good condition? Yes – go to step 2. No – repair the wiring/connectors and retest.
- 22. Check the engine coolant level. Is it within the normal range? Yes – go to step 3. No – top off the coolant, then retest after reaching operating temperature.
- 33. Measure the voltage at the coolant temperature sensor connector with a multimeter. Is it between 0.5V and 4.5V? Yes – go to step 4. No – replace the coolant temperature sensor.
- 44. Using diagnostic software, check the coolant temperature reading. Is it within expected limits when the engine is at operating temperature? Yes – ECM may be at fault, consider replacement. No – replace the coolant temperature sensor.
Common causes
- Bad engine coolant temperature sensor
- Corroded or damaged wiring
- Faulty connectors
- Low coolant level
- Faulty engine control module (ECM)
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It’s advisable to fix this soon as it could lead to engine overheating.
Will this code come back after fixes?
If repaired properly, it should not return.
Why does this code sometimes pair with other sensor codes?
If multiple sensors fail or wiring issues exist, they can trigger multiple fault codes.
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