Engine Coolant Temperature Sensor 1
The engine coolant temperature sensor is reporting a fault.
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 engine's computer uses a sensor to measure how hot the engine coolant is. If it gets too low or high a signal can get thrown that there’s a problem with how the sensor works or the coolant itself.
What the computer is actually seeing
The ECM expects input from the engine coolant temperature sensor to be between -40°C and 130°C (-40°F to 266°F). If it gets readings outside this range, it triggers the fault code.
What a healthy reading looks like
Normal operating range for engine coolant temperature is 85°C to 105°C (185°F to 221°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. Check the wiring and connectors for the coolant temperature sensor for any damage or corrosion. Repair as necessary. Decision point: Is wiring intact? Yes: Go to step 2. No: Repair wiring and retest.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues or connector corrosion
- Coolant leaks affecting the sensor readings
- ECM calibration issue
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
You can drive, but it's best to fix this soon to avoid overheating issues.
Will the code come back?
If the root cause isn't addressed, yes it will return.
Why does it pair with SPN 126?
SPN 125 and SPN 126 are often related to engine temperature issues and sensor reliability.
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