Engine Cooling System Temperature
Indicates that the engine cooling system temperature is out of range.
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What it means (plain English)
The engine temperature is either too high or too low, which can lead to overheating or poor performance. This can happen if the coolant is low or if the thermostat is stuck.
What the computer is actually seeing
The ECM monitors the engine coolant temperature (ECT) sensor, looking for values between 160°F and 220°F (70°C and 105°C) under normal operating conditions. Anything outside this range triggers the code.
What a healthy reading looks like
Normal ECT should be between 160°F and 220°F. If the temperature exceeds 230°F (110°C), the engine will enter protection mode.
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 coolant level in the reservoir. Add coolant if necessary. Decision: If level is low, fill and retest; if not, proceed to Step 2.
- 22. Inspect the ECT sensor wiring and connector for damage or corrosion. Decision: If issues are found, repair or replace; if not, proceed to Step 3.
- 33. Measure the resistance of the ECT sensor at various temperatures. Use your scan tool to compare actual temperature readings. Decision: If readings are inconsistent, replace the ECT sensor; if consistent, proceed to Step 4.
- 44. Check the thermostat function by examining the engine temperature during warm-up. Decision: If the thermostat opens too late or stays closed, replace it; if it functions correctly, further diagnosis might be needed.
Common causes
- Low coolant level
- Faulty coolant temperature sensor
- Wiring or connector issues to the ECT sensor
- Thermostat stuck closed or open
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to address this issue soon, as driving can lead to engine overheating.
Will the code come back after I clear it?
If the issue isn't resolved, the code will likely return once the engine reaches operating temperature.
Why does this code come up with SPN 112?
SPN 112 is often related as it also involves engine temperature readings, so they can trigger together.
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