Engine coolant temperature circuit high input
The coolant temperature circuit input is above its expected electrical range. In typical thermistor circuits, high voltage can appear as extremely cold coolant, including when a circuit is open. High input does not mean high actual coolant temperature, and an unreliable reading cannot establish that the engine is safely cool.
Can I keep driving?
A temperature warning, steam, coolant smell or coolant loss requires pulling over safely, shutting down and arranging assistance; never open a hot cooling system. If the reading is unreliable even without symptoms, ask a shop to assess the vehicle before further driving.
Flashing light, burning smell or smoke? Pull over safely. Danger to life: call 911.
What does this code mean for your car?
The same code can need different checks depending on the model and engine. Enter your vehicle details to find relevant sources and checks.
Symptoms
- Implausible temperature reading or unusual cooling fan behavior
- Hard starting or uneven idle
- Check engine light, sometimes with a temperature warning
Possible causes
- 1Open signal wire or disconnected coolant temperature sensor connector
- 2Coolant temperature sensor with an internal open circuit or excessive resistance
- 3Ground or signal circuit fault
- 4Coolant condition or cooling-system trouble affecting measurement reliability
These possibilities are not ranked by frequency and do not diagnose your vehicle.
Checks you can safely do yourself
Safe checks only: engine off and cold, car on level ground.
- Save all codes and any freeze-frame data your scanner displays before clearing or repairs.
- Only with the engine fully cold, view the level through a translucent coolant reservoir if fitted; do not open a cap or touch the fan, which can start automatically.
When you need a shop
Ask the shop to compare reported and actual temperature using professional equipment, test the sensor circuit and response, and verify cooling system and fan operation. A cold scanner reading cannot rule out overheating when the circuit is faulty.
How much does it cost?
A US repair estimate needs a diagnosis and a local shop quote.
We do not have a verified US repair quote for this fault. Request 2-3 itemized estimates after diagnosis; vehicle, parts and labor determine the cost.
Get 2-3 quotes
Investigate this code for my carFAQ
Can I keep driving with P0118?
A temperature warning, steam, coolant smell or coolant loss requires pulling over safely, shutting down and arranging assistance; never open a hot cooling system. If the reading is unreliable even without symptoms, ask a shop to assess the vehicle before further driving.
What can cause this code?
Possibilities include open signal wire or disconnected coolant temperature sensor connector; coolant temperature sensor with an internal open circuit or excessive resistance; ground or signal circuit fault; coolant condition or cooling-system trouble affecting measurement reliability. The code does not rank causes or identify a part that must be replaced.
Does clearing the code fix the fault?
No. Clearing the code does not repair its cause or prove the fault is absent. It can erase diagnostic data and reset readiness monitors. Even if the code does not reappear immediately, the repair needs verification using the tests appropriate to the vehicle.
What if this code appears during a pre-purchase check?
Arrange an independent professional inspection before buying, including stored data, readiness status and written diagnostic findings. Ask the shop to compare reported and actual temperature using professional equipment, test the sensor circuit and response, and verify cooling system and fan operation. A cold scanner reading cannot rule out overheating when the circuit is faulty.
How much does repairing P0118 cost?
We do not have a verified US repair quote for this fault. Request 2-3 itemized estimates after diagnosis; vehicle, parts and labor determine the cost.