Abnormal Engine Temperature Signal
The engine control module is receiving a temperature signal that is outside the expected range.
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What it means (plain English)
The engine computer is getting weird temperature readings from the engine temperature sensor, like way too hot or too cold, which can mess with how the engine runs.
What the computer is actually seeing
The engine control module (ECM) monitors the engine temperature sensor output voltage. Normal readings should be between 0.5V (cold) and 4.5V (very hot). If the signal drops below 0.5V or exceeds 4.5V, the ECM flags this issue as SPN 4685.
What a healthy reading looks like
Expected sensor voltage should range from 0.5V to 4.5V under normal operating conditions.
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. Check the engine coolant level. Ensure it is within the specified range: low coolant can cause inaccurate temperature readings.
- 22. Inspect connectors and wiring for the engine temperature sensor for damage or corrosion. Repair or replace as necessary.
- 33. Measure the voltage at the engine temperature sensor with a multimeter. Expect a voltage between 0.5V and 4.5V, depending on engine temperature.
- 4 - If voltage is outside this range, proceed to step 4.
- 5 - If voltage is within range, suspect ECM issues.
- 64. Test or replace the engine temperature sensor with a known good part.
- 75. Clear codes and run the engine to see if the fault returns. If it does, replace the ECM.
Common causes
- Faulty engine temperature sensor
- Bad wiring or connectors to the sensor
- Incorrect coolant level or condition
- ECM calibration issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive, as incorrect temperature readings can lead to engine damage.
Will this code come back after clearing it?
If the root issue isn't fixed, yes, it's likely to return.
Why does this code sometimes pair with SPN 469?
SPN 469 also relates to temperature sense and could indicate a systemic issue with the temperature sensing circuit.
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