P0117: How to Diagnose & Fix — Engine Coolant Temperature Sensor Circuit Low
15 vehicles · 10 makes · $30-$7,000 repair
How to diagnose and fix P0117: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Ford Flex · 2009–2019
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.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (2)
Chevrolet Sonic · 2012–2020
The Chevrolet Sonic across all model years is prone to premature water pump failure. The water pump on the Ecotec engines (both 1.4T and 1.8L) can begin leaking coolant between 40,000-80,000 miles. On the 1.4T, the water pump is driven by the timing chain, so failure can lead to more serious engine damage if coolant loss goes unnoticed. The 1.8L has a belt-driven pump that is easier and cheaper to replace.
Common Symptoms
- Coolant level dropping between fills
- Visible coolant leak under vehicle
- Engine temperature gauge running higher than normal
- Sweet smell from engine bay (coolant odor)
- Whining or grinding noise from water pump bearing
How to Fix
Replace the water pump at the first sign of leaking. On the 1.4T, the water pump is internal and driven by the timing chain, making replacement more labor-intensive ($400-$800). On the 1.8L, it is belt-driven and easier to access ($200-$400). Monitor coolant levels regularly. Replace the thermostat at the same time.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Engine Water PumpCross-refWPK-818
Fitment confirmed against the ShowMeTheParts catalog for this vehicle's year and engine.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (1)
MINI John Cooper Works · 2008–2024
MINI JCW models across all generations suffer from premature water pump failure and cracking plastic thermostat housings. The thermostat housing is made entirely of plastic, which degrades from heat cycling and eventually cracks, causing coolant leaks. The water pump bearings and seals typically fail between 50,000-80,000 miles. Undetected coolant loss from either failure can lead to overheating and severe engine damage, especially on the turbocharged JCW engines that generate significant heat.
Common Symptoms
- Coolant puddle under the vehicle after parking
- Engine temperature gauge reading higher than normal
- Low coolant warning light illuminating
- Sweet smell of coolant from engine bay
- Visible coolant seepage around water pump or thermostat housing
How to Fix
Proactively replace the water pump and thermostat housing together at 60,000-70,000 miles as preventative maintenance, even if no symptoms are present. The job costs $500-900 at an independent MINI shop. Use an aluminum aftermarket thermostat housing if available for your generation to eliminate the plastic cracking issue. Check for coolant seepage under the car regularly and monitor the coolant level and temperature gauge closely.
Owner tips & cautions
- TipReplace the water pump, thermostat housing, and all coolant hoses as a package at 60K miles — doing them separately means paying twice for labor since they all share the same access area. Budget $700-900 for the full cooling system refresh.
Sources for this issue (2)
- MINI JCW Water Pump Replacement — MiniF56.comowner-report
- Common R56 MINI Problems — JCW Adventuresowner-report
Nissan NV · 2012–2021
Volvo V90 Cross Country · 2017–2022
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P0117 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 P0117 mean?
P0117 stands for "Engine Coolant Temperature Sensor Circuit Low." This code means the engine coolant temperature (ECT) sensor is reading too low a voltage, which the computer interprets as an impossibly high coolant temperature. In most cases this is an electrical fault — such as a short to ground in the wiring — rather than the engine actually overheating. The coolant temperature signal affects fuel mixture, cooling fans, and other functions, so a bad reading can cause poor running, hard starting, or fans running constantly. The fault is usually in the sensor or its wiring.
What are the most common causes of P0117?
The most common causes of P0117 are: Faulty engine coolant temperature sensor, Short to ground in the sensor signal wire, Damaged or corroded wiring/connector at the sensor, Coolant contamination affecting the sensor, Poor electrical ground, Faulty PCM/ECM (less common). The specific cause varies by vehicle.
How much does it cost to fix P0117?
Repair costs for P0117 range from $30 to $7,000, depending on the vehicle and root cause.
Which vehicles are affected by P0117?
Au7o has documented P0117 across 15 vehicle models from 10 manufacturers: Cadillac, Chevrolet, Chrysler, Dodge, Ford, MINI, Nissan, Subaru, Volkswagen, Volvo.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.