P0118 on Ford: How to Diagnose & Fix
Engine Coolant Temperature Sensor Circuit High
1 Ford model · 1 documented issue · 1 critical · $1,500-$7,000 repair
P0118 on Ford by model: symptoms, diagnosis and fix
The 3.5L Duratec and 3.5L EcoBoost V6 engines in the Ford Flex have a critical design flaw: the water pump is driven by the timing chain and mounted internally inside the engine. When the water pump seal fails, coolant leaks directly into the engine oil, creating a milky sludge that destroys engine bearings in a matter of miles. Because the pump is internal, there is no external leak to warn the owner — the first symptom is often catastrophic engine failure. This is one of the most expensive and common failures on high-mileage Flex vehicles, with repair quotes ranging from $5,000 to $7,000+ for engine replacement.
Common Symptoms
- Milky or frothy substance on oil dipstick or under oil fill cap
- Sweet smell from engine oil indicating coolant contamination
- Coolant level dropping with no visible external leak
- Engine overheating
- Low oil pressure warning light
- Knocking or ticking sound from engine indicating bearing damage
- White or sweet-smelling exhaust
How to Fix
Proactively replace the water pump and timing chain as preventive maintenance between 100,000-120,000 miles ($1,500-$2,500 labor-intensive job). Check oil regularly for milky appearance or coolant smell — catching it early can save the engine. If coolant is found in the oil, stop driving immediately and have it towed. Use only Ford-approved coolant to minimize seal degradation. Consider extended warranty coverage when purchasing a high-mileage Flex.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Engine Water PumpCross-refWPFD-609V
Fitment confirmed against the ShowMeTheParts catalog for this vehicle's year and engine.
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Sources for this issue (1)
P0118 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0118 mean on a Ford?
P0118 stands for "Engine Coolant Temperature Sensor Circuit High." P0118 indicates the engine coolant temperature (ECT) sensor circuit is reading abnormally high voltage, which the computer interprets as an implausibly cold coolant temperature. The ECT sensor changes resistance with temperature and tells the PCM how hot the engine is so it can manage fuel, the cooling fans, and the gauge. High voltage on this circuit usually points to an open circuit or a sensor reporting an unrealistically low temperature. The car may run rich, struggle to enter closed-loop operation, idle poorly, or show an inaccurate temperature gauge. On Ford it is documented across 1 model: Flex.
What are the most common causes of P0118?
The most common causes of P0118 are: Faulty (open) engine coolant temperature sensor, Open or broken wire in the ECT signal circuit, Loose, corroded, or disconnected sensor connector, Poor ground or open in the sensor return circuit, Damaged wiring harness near the sensor, Corrosion in the connector terminals, Failed PCM input (rare). The specific cause varies by vehicle.
How much does it cost to fix P0118 on a Ford?
Published repair estimates on Ford range from $1,500 to $7,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0118 on a different make?
View P0118 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.