P0118: Engine Coolant Temperature Sensor Circuit High
Key takeaways
- P0118 means the coolant temperature sensor's signal voltage is above its normal range, which the computer reads as an impossibly cold engine.
- It is almost always an open circuit: an unplugged or corroded connector, a broken wire, or a sensor that has failed open.
- While the code is set, the cooling fan may run all the time, the engine may run rich, and a dash gauge fed by the same sensor can stop warning you about real overheating.
- Unplugging the sensor and jumping the connector tells a shop in minutes whether the sensor or the wiring is at fault; a sensor is $80–$250 installed.
- Ford and Lincoln bulletins for 2.7L, 2.3L and 3.0L EcoBoost engines trace P0118 and its sister codes to the sensor connector, its wiring or the sensor itself.
What P0118 means
Your engine computer is getting a coolant temperature signal so high it would mean the engine is colder than any running engine gets, so it has stopped trusting the sensor. The scanner name is Engine Coolant Temperature Sensor Circuit High. The coolant temperature sensor is a thermistor: its resistance rises as the coolant gets colder, which pushes the signal voltage up toward the 5-volt reference. When that voltage sits above the top of its normal range, the computer sets P0118. In practice that almost always means the circuit is open somewhere: a connector that’s unplugged or corroded, a broken wire, or a sensor that has failed open inside.
Is it safe to drive?
Yes, in most cases, while you get it fixed. Once the code sets, the computer ignores the sensor and runs on a substitute value. Most cars switch the cooling fan on full-time as a precaution. Depending on how your car fills in the missing reading, the engine may run rich, idle rough, or use noticeably more fuel. The bigger catch: if your temperature gauge uses the same sensor, it may sit at cold and won’t warn you if the engine really does overheat. What changes the answer: steam, coolant boiling over, a sweet smell, or the heater suddenly blowing cold. Then stop, let it cool, and read car overheating.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Sensor connector unplugged, loose or corroded | Code clears or changes when the connector is wiggled or reseated; green corrosion or coolant in the plug | $100–$250 |
| Sensor failed open | Jumping the two connector terminals makes the reading swing to very hot (P0117); resistance out of spec or infinite | $80–$250 |
| Broken signal or ground wire | Reading stays at very cold with the connector jumped; continuity check finds the break | $100–$250 |
| Damaged engine harness section | Break sits in a harness run at the cylinder head or under the intake; several sensor codes at once | $250–$600 |
| Sensor or harness design issue (some makes) | A bulletin for your exact model and year names P0118 | $80–$600, often covered by the bulletin |
What to check first
- Check the coolant level with the engine cold. A low level won’t set P0118 on its own, but you want to know the engine isn’t also losing coolant while the gauge can’t warn you.
- Look at the scan tool reading. A value pinned at the bottom of the scale (often -40°F) on a warm engine confirms a false signal.
- Check the connector. Make sure it’s fully seated and the lock tab is engaged, and look for corrosion or coolant in the plug. Recent work near the thermostat or intake is a common reason it’s loose.
- Jump the connector and watch the reading. If it swings to very hot, the wiring is good and the sensor is open. If it stays cold, the break is in the wiring.
- Look up bulletins. Every bulletin naming P0118 is Ford or Lincoln: 2015–2020 2.7L EcoBoost engines (F-150, Edge, Fusion, MKX, Nautilus, Continental) and 2020 Explorer and Aviator with the 2.3L or 3.0L. They trace it to an unseated sensor connector, damaged wiring, or the sensor, and one F-150 fix relocates the sensor into a new heater hose with a jumper harness.
- Clear the code and drive after any connector repair; it should stay off once the circuit is sound.
What it costs
The cheap outcome is a new sensor at $80–$250 installed; some are buried under intake parts and sit at the top of that range. The common outcome is a connector or wire repair at $100–$250. The expensive outcome is a damaged section of engine harness, up to about $600. Jumping the connector during a $100–$180 diagnosis tells a shop quickly whether you need the sensor or the wiring, so you don’t pay for a part that wasn’t the problem.
Related codes
P0118 is the high-side twin of P0117 (the same circuit reading low). It can appear with P0116 and P0119 (range and intermittent faults on the same sensor), and a car that also sets P0125 or P0128 may simply be getting a bad temperature reading rather than warming up slowly. If the fan runs nonstop and the gauge climbs at stoplights, see car overheating at idle.
What owners report to NHTSA
3 complaints filed with NHTSA mention P0118, 2 of them since 2015, across 3 different models. The component owners most often filed it under: engine and engine cooling:cooling system.
Manufacturer service bulletins that name P0118
13 technical service bulletins and manufacturer communications filed with NHTSA mention P0118, from 2 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- FORD EXPLORER (2020), bulletin 10177711: Some 2020 Explorer/Aviator vehicles equipped with a 3.0L EcoBoost engine may exhibit an illuminated malfunction indicator lamp (MIL) and/or Engine Coolant Over Temperature warning with diagnostic trouble codes (DTCs) P01…
- LINCOLN AVIATOR (2020), bulletin 10177711: Some 2020 Explorer/Aviator vehicles equipped with a 3.0L EcoBoost engine may exhibit an illuminated malfunction indicator lamp (MIL) and/or Engine Coolant Over Temperature warning with diagnostic trouble codes (DTCs) P01…
- FORD EDGE (2015, 2016, 2017, 2018), bulletin 10177705: Some 2015-2020 F150/Edge/Fusion, 2016-2018 MKX, 2019-2020 Nautilus, and 2017-2020 Continental vehicles equipped with 2.7L EcoBoost engines may exhibit an illuminated malfunction indicator lamp (MIL) and/or Engine Coolant…
- LINCOLN CONTINENTAL (2017, 2018, 2019, 2020), bulletin 10177705: Some 2015-2020 F150/Edge/Fusion, 2016-2018 MKX, 2019-2020 Nautilus, and 2017-2020 Continental vehicles equipped with 2.7L EcoBoost engines may exhibit an illuminated malfunction indicator lamp (MIL) and/or Engine Coolant…
- FORD F-150 (2018, 2019, 2020), bulletin 10198582: Some 2018-2020 F-150 vehicles equipped with a 2.7L EcoBoost engine may exhibit an illuminated malfunction indicator lamp (MIL) and/or Engine Coolant Over Temperature warning with diagnostic trouble codes (DTCs) P0116, P0…
- FORD FUSION (2017, 2018, 2015, 2016), bulletin 10127410: Some 2015-2018 F150/Edge, 2016-2018 MKX and 2017-2018 Fusion, Continental vehicles equipped with a 2.7L engine may experience a malfunction indicator lamp (MIL) and/or wrench lamp with Diagnostic Trouble Codes (DTCs): P0…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Is my engine really that cold if I have P0118?
No. P0118 means the signal is higher than any running engine should produce, which the computer reads as something like -40°F. That points to an open circuit, such as an unplugged connector, a broken wire or a dead sensor, not a real temperature.
Can P0118 hide real overheating?
It can. If your dash gauge uses the same sensor, it may sit at cold no matter how hot the engine gets. Until it's fixed, watch for steam, a sweet smell, or the heater suddenly blowing cold, and check the coolant level when the engine is cold.
Why does my car run rough or use more fuel with P0118?
A cold engine needs extra fuel, so a false cold reading can make the computer add fuel it doesn't need. On many cars the substitute value limits this, but you may still notice worse mileage, a fuel smell or a lumpy idle.
What's the difference between P0118 and P0117?
They're opposite ends of the same circuit. P0118 means the signal is too high (reads very cold), usually an open circuit. P0117 means it's too low (reads very hot), usually a short to ground.
How much does it cost to fix P0118?
A connector or wire repair is $100–$250, a new sensor $80–$250, and replacing a damaged section of engine harness up to about $600 at an independent shop.