Engine Control Module (ECM) Temperature Sensor Circuit Range/Performance Problem
The ECM has detected a problem with the temperature sensor's performance.
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 computer that controls your engine has a sensor to check how hot it is. If the sensor gives readings that are too high or too low for too long, the computer throws this code.
What the computer is actually seeing
The ECM expects the temperature sensor to provide readings within a normal range (typically between 180°F and 220°F for engine operation), but it sees values that are out of this range or not changing as expected.
What a healthy reading looks like
Normal engine temperature readings should be within 180°F to 220°F (82°C to 104°C). If readings go below 140°F (60°C) or exceed 250°F (121°C), the ECM will flag a P0618.
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 for any related codes. If other codes exist, address those first as they may be related. Decision Point: Are there other codes? If yes, diagnose those first.
- 22. Inspect the wiring and connectors related to the temperature sensor. Look for damage, corrosion, or loose connections. Decision Point: Is the wiring intact? If no, repair or replace wiring as necessary.
- 33. Measure the resistance of the temperature sensor at ambient temperature (should be around 2.5K ohms at 77°F). Decision Point: Is the sensor reading within specifications? If no, replace the temperature sensor.
- 44. Clear the code and run the engine to see if the temperature readings return to a normal range. Decision Point: Does the code return? If yes, suspect a faulty ECM or further electrical issues.
Common causes
- Faulty ECM temperature sensor
- Wiring issues in the temperature sensor circuit
- Faulty ECM
- Poor electrical connections or corroded connectors
- Programming errors in the engine control module
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, it's drivable but should be fixed soon to avoid potential engine overheating.
Will this code come back after clearing it?
If the underlying issue isn't fixed, it will likely return.
Why does this code pair with other codes?
Related codes often indicate issues with the same system, like the coolant temperature sensor or ECM faults.
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 →