FMI 7 - G8 - Engine Coolant Temperature Sensor - Voltage Above Normal
The engine coolant temperature sensor is reporting a voltage that is higher than expected.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The coolant temperature sensor is telling the computer that the engine is running hotter than it really is, possibly due to a wiring issue or a faulty sensor itself.
What the computer is actually seeing
The engine control module (ECM) reads a voltage signal from the coolant temperature sensor. Normally, when the engine is cold, the sensor sends around 0.5 volts (representing coolant temperatures below 140°F). As the engine warms up, voltages increase up to about 4.5 volts at temperatures above 230°F. A voltage higher than 4.5 volts triggers this code.
What a healthy reading looks like
0.5V to 4.5V depending on engine temperature.
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 connector at the coolant temperature sensor for damage or corrosion.
- 2Inspect the harness for any visible shorts or breaks, and verify the continuity of the wires.
- 3With the engine off, use a multimeter to measure the voltage at the sensor connector. It should be around 0.1 to 0.5 volts with the ignition on but engine off.
- 4Start the engine and monitor the coolant temperature sensor voltage as the engine warms up. It should rise steadily to about 4.5 volts as it reaches operating temperature. If it exceeds 4.5 volts, proceed to the next step.
- 5Replace the coolant temperature sensor if the wiring is good and the voltage is outside normal range.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues (shorts or opens in the harness)
- Poor connector condition
- ECM software error
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive for long as it could lead to overheating issues.
Will the code come back after clearing it?
If the underlying issue isn't fixed, yes, the code will likely return.
Why are other codes present with this one?
Other faults can cause or contribute to incorrect readings from the temperature sensor.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →