MotorBitP0118: Engine Coolant Temperature Sensor 1 Circuit High
Coolant temp circuit high (often -40 reading). Fans, mixture, and gauge can all be wrong.
Educational OBD2 information. Confirm on your vehicle with a scan tool. MotorBit can read this code, freeze frame, and live data over an ELM327 adapter.
What P0118 means
ECT resistance looks open. The PCM thinks the engine is extremely cold.
Why the check engine light comes on
A false cold reading keeps the engine in open-loop rich, raising emissions and washing cylinders.
Common causes
- Failed ECT sensor
- Open wiring
- Corroded connector
Typical symptoms
- High idle
- Rich smell
- Gauge may read cold
- Heater issues
What to do next
- Read coolant temp in MotorBit. -40°C/-40°F almost always means an open circuit.
- Test the sensor and harness before replacing the thermostat.
How MotorBit helps
Open MotorBit, connect your ELM327, and read P0118 with freeze frame (RPM, load, temperature, speed at the moment the fault set). Then watch live PIDs and fuel trims instead of replacing parts by guesswork. When the repair is verified, clear the code and re-check monitors.
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FAQ
Is P0118 serious?
Severity is listed as medium on this page. Misfire, crank/cam, and communication codes deserve faster attention than a tiny EVAP leak.
Will disconnecting the battery clear P0118?
It may hide the lamp temporarily, but the fault usually returns and you lose freeze-frame evidence. Scan first, then clear after the repair.
Can MotorBit clear P0118?
Yes, after you understand the cause. Clearing without a repair is how the light comes back on the next drive cycle.