Engine Coolant Temperature (ECT) Sensor Voltage Low
The engine coolant temperature sensor is reporting a lower than expected voltage.
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What it means (plain English)
The ECT sensor is sending a signal to the engine control module (ECM) that the engine coolant is too cold, usually below 0.5 volts, which could cause the engine to run rich and increase emissions.
What the computer is actually seeing
The ECM expects the ECT sensor voltage to be in a specific range (typically 0.5 to 4.5 volts). If the voltage drops below 0.5 volts, the ECM triggers this fault code.
What a healthy reading looks like
Normal ECT sensor voltage should be between approximately 0.5 and 4.5 volts depending on engine temperature. Cold engine should be around 0.5 volts, and as the engine warms up, the voltage should rise.
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.
- 1Check the engine coolant level first; it should be at the proper level for the vehicle specifications.
- 2Inspect the wiring and connector for the ECT sensor for any signs of damage or corrosion. Repair as necessary.
- 3Using a multimeter, measure the voltage at the ECT sensor connector. If it's below 0.5 volts, the sensor may be faulty or there's a wiring issue.
- 4If the voltage is normal, check the sensor's ground. The ground should read close to 0 ohms to the battery negative.
- 5If all checks are okay and the code persists, consider replacing the ECT sensor.
Common causes
- Faulty engine coolant temperature sensor
- Open or shorted wiring in the ECT circuit
- Poor connection or corroded terminals
- Insufficient coolant level
- ECM malfunction
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally safe to drive, but you may experience higher emissions and reduced fuel efficiency until it's fixed.
Will this code come back after resetting?
It may return if the underlying issue isn't resolved, such as a faulty sensor or bad wiring.
Why does this code often pair with SPN 160?
Both codes relate to coolant temperature sensor issues; they can trigger together if the sensor misreads temperature.
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