| Table of Contents | |
| Possible Causes of P0118 & Their Repair Costs | DTC P0118 signals that the engine control module detects an abnormally high voltage from the coolant temperature sensor circuit. |
| How to Diagnose the Cause of Your P0118 Code | A P0118 code is triggered when the engine control module detects a high voltage condition in the coolant temperature sensor circuit. The most common causes include a faulty ECT sensor, damaged or corroded wiring, contaminated coolant, or, rarely, a defective engine control module. |
| Can I drive with a P0118 code? | No. Driving with a P0118 code is not recommended, as it can cause severe engine overheating and expensive damage to critical components. |
| DIY | How To Fix P0118 Causes |
DIYable P0118 triggers include: Contaminated Coolant Other DIY Considerations for Code P0118 |
| P0118 Code FAQs |
Frequently asked questions: What makes and models does code P0118 affect the most? What causes a P0118 code? Does P0118 affect Chevy vehicles? What about Nissans? |
The cooling system is one of the most vital elements in keeping a car engine functioning. High heat kills engines, and properly flowing coolant helps prevent this. Measuring coolant temperature is part of the process, where the engine coolant temperature (ECT) sensor comes into play.
Most cars have one ECT sensor near the cylinder head or thermostat housing. Some vehicles also have a second ECT sensor, often adjacent to the radiator. Although rare, some cars have three sensors.
Code P0118—Engine Coolant Temperature Sensor Circuit High Input is part of a diagnostic trouble code (DTC) family that involves circuitry issues with the ECT sensor. P0118 indicates a high voltage condition, while P0117 is centered around low voltage. P0119 signals voltage that fluctuates outside the normal range.
The check engine light surfaces for a P0118 code when the engine control module (ECM) or powertrain control module (PCM) detects a high voltage condition with the ECT sensor. This is often due to an open circuit, which can be caused by several conditions, which we’ll review in detail.
Engine temperature isn’t something to be trifled with. Running a car under high-temperature conditions for even a short period can lead to catastrophic engine damage. In short, driving with a P0118 code is ill-advised for this very reason. Paying for a tow truck is much cheaper than replacing a cracked engine block or damaged head gasket.
While a bad ECT sensor is usually at the heart of a P0118 code, other problems can be the cause. We’ll examine the most common symptoms and review the associated repairs, including DIY options. You’ll also learn what vehicles are most susceptible to P0118-related issues.
Possible Causes of P0118 & Their Repair Costs
While replacing an engine coolant temperature sensor isn’t the most expensive repair job, it still can cost close to $500 through a mechanic. Still, it makes sense to rule out other possible reasons for a P0118 code.
Check out the FIXD article on the most common causes of check engine lights.
Here’s a look at the parts most likely involved with a P0118 code and how much things cost. Note that actual prices depend on the vehicle and location.
P0118 Code Triggers & Typical Repair Costs
| Part To Repair | Part / DIY Price | Mechanic Total Cost |
| Engine Coolant Temperature (ECT) Sensor | $97–$122 | $406–$448 |
| Coolant (flush) | $111–$129 | $238–$283 |
| ECT Sensor Wiring | $25–$100 | $100–$350 |
| Engine Control Module (ECM)/Powertrain Control Module (PCM) | $929–$978 | $1,006–$1,075 |
Here’s how different malfunctioning parts can trigger a P0118 code.
Parts Most Likely to Fail & Cause a P0118 Code
| Parts that can cause P0118 | How it could cause P0118 |
| Engine Coolant Temperature (ECT) Sensor | A P0118 code is triggered when the Engine Control Module (ECM) detects a higher-than-normal voltage reading from the ECT sensor, which commonly occurs if the ECT sensor fails internally. |
| Coolant | Contaminated or degraded coolant can create electrical interference or deposit buildup around the ECT sensor’s thermistor (a temperature-sensitive resistor), causing inaccurate resistance readings that the ECM interprets as abnormally high temperatures, generating a P0118 code. |
| ECT Sensor Wiring | A P0118 code can occur when an open circuit or break in the ECT sensor wiring occurs. This causes the ECM to see a high-voltage signal instead of the normal resistance-based temperature reading. Damaged connectors, broken wires, or corroded terminals in the ECT circuit can all create this open circuit condition. |
| Engine Control Module (ECM)/Powertrain Control Module (PCM) | A faulty ECM/PCM may misinterpret normal voltage signals from a functioning ECT sensor as being too high or having internal circuit issues with temperature signal processing, resulting in a false P0118 code even when the sensor and wiring are working correctly. This is a rare situation. |
Makes Commonly Affected By P0118
FIXD sensor data shows that Chevrolets are the most affected brand for P0118 codes, with the Traverse at the top of the list. The Impala follows closely, but both vehicles have medium occurrence ratings for this problem. The Malibu takes the third spot but at a low incident level. Interestingly, Chevy’s best-selling vehicle, the venerable Silverado 1500 pickup, has no history of P0118 codes.
Honda has only one vehicle on this top-five roster, but the frequency of P0118 codes is enough to earn the Pilot crossover second-place status. Meanwhile, Dodge slides into third place, with the Grand Caravan being the worst of the worst for this Mopar brand. This minivan is one of the few vehicles with an overall high occurrence rating among all the models analyzed. The Charger and Ram 1500 are no strangers to P0118 codes but nowhere near the frequency of the Grand Caravan.
While most of the Fords susceptible to P0118-related issues are pickups, the F-150 doesn’t share this experience. Like its Chevy counterpart, this full-size truck doesn’t have a background with this code. The dishonor rests with the smaller Ranger, followed by the Escape crossover. The F-350 takes third.
At the same time, Buick lands fifth among all automakers, with P0118 codes prevalent. The Enclave, a platform-mate with the Chevrolet Traverse, is the Buick with the greatest number of P0118 codes but a medium incident rating. The old-school LaCrosse and LeSabre sedans are also among the most vulnerable Buicks.
| Top 5 Makes Affected by P0118 | Most Affected Model(s) |
|
Chevrolet |
Traverse |
| Impala | |
| Malibu | |
| Honda | Pilot |
|
Dodge |
Grand Caravan |
| Charger | |
| Ram 1500 | |
|
Ford |
Ranger |
| Escape | |
| F-350 | |
|
Buick |
Enclave |
| LaCrosse | |
| LeSabre |
How to Diagnose the Cause of Your P0118 Code
Discovering the reason behind a check engine light requires an OBD-II scanner. Your options include the FIXD plug-in sensor and accompanying app that shows the diagnostic trouble code, live data, and common causes behind the problem. Alternatively, a basic code reader that plugs into your car’s OBD-II port will also work, but these devices only show the code, not the underlying issue that triggered the code. Plus, a basic reader doesn’t offer live data streaming, which can help diagnose a P0118 code.
Beyond a basic inspection (as outlined above), a novice can use live data to confirm if the ECT sensor is functioning. It’s a relatively simple process. Turn the car off and allow the engine to cool. Plug in the scanner and turn the ignition to the “on” position without starting the engine. Access the live data for the ECT sensor and the intake air temperature. They should both have similar readings. However, a significantly different temperature measurement from the ECT sensor indicates that you’ve probably found what’s causing the P0118 code.
Keep these other steps in mind when inspecting for other code P0118 triggers.
- Have the right tools for a basic inspection: a flashlight, gloves, safety goggles, and a rag.
- Park on a safe, level surface.
- Turn the car off and engage the parking brake.
- Allow the engine to cool.
Symptoms of P0118 Causes
Most P0118-related repairs require next-level DIY skills, but there are still steps just about anyone can take to start the ball rolling. At the very least, you’ll be a much better-informed car owner when arriving at the service center.
Symptoms:
- Check Engine Light illuminated
- Hard starting when the engine is cold
- Electric cooling fan constantly runs, especially at startup
- Poor heater performance
- Engine may take longer to warm up
What to Inspect:
Locate the ECT sensor and conduct a basic inspection:
- Check for visible damage to the sensor and surrounding area
- Look for broken wires or damaged connectors
- Inspect for coolant leaks around the sensor
- Check the coolant level in the reservoir
- Use a scanner with live data capability to compare ECT sensor readings with other temperature sensors (see above, How to Diagnose the Cause of Your P0118 Code, for more details)
Safety Note: Only inspect when the engine is cold, and avoid removing the sensor yourself, as it can cause coolant loss.
Symptoms:
- Unusual gauge temperature readings
- Engine running hotter than normal
- Sweet or unusual smell from the engine
- Visible rust or oil in coolant
- Thick, discolored, or sludgy coolant
- Visible particles floating in coolant
- Poor heater performance
- Engine overheating
What to Inspect:
With a cold engine, check the coolant reservoir or radiator (if safe to open) and:
- Look at the coolant color—it should be bright green, orange, or pink (depending on the type)
- Check for floating particles or debris
- Look for oil sheen on the coolant surface
- Inspect for rust color or milky appearance
- Smell the coolant—it should not have a burnt odor
- Check coolant level for proper fill
Safety Note: Never open a hot radiator or reservoir; dispose of used coolant properly at an auto parts store or recycling center.
Symptoms:
- Intermittent check engine light
- Erratic temperature gauge readings
- Temperature readings that seem impossible (too high/low)
- Engine fan turns on and off randomly
What to Inspect:
With the engine off, locate the ECT sensor and follow its wiring harness.
Basic inspection points:
- Look for any visible wire damage
- Check for loose or corroded connections
- Inspect for wires rubbing against engine parts
- Look for brittle, cracked, or melted insulation
- Check connector pins for corrosion or damage
Safety Note: Don’t disconnect any electrical connectors or remove wiring covers unless you’re familiar with automotive electrical systems.
Symptoms:
- Multiple random check engine codes appearing
- Engine performance issues that come and go
- Erratic readings from multiple sensors
- Inconsistent starting behavior
- Random stalling or misfiring
- Unexpected changes in transmission behavior
- Poor fuel economy without other apparent causes
What to Inspect:
This is primarily a job for a professional mechanic, but there are some basic checks you can make.
Essential DIY steps include:
- Check if multiple warning lights appear randomly
- Look for water damage or corrosion on visible ECM parts
- Note if clearing codes results in the immediate return of the same or different codes
- Document all unusual behaviors to tell your mechanic
A professional diagnosis is needed because:
- ECM testing requires specialized equipment
- Multiple sensors need to be tested to rule out other causes
- Complex diagnostic procedures are required
- ECM replacement often needs professional programming
Safety Note: Don’t attempt to remove or test the ECM yourself, as this could cause additional problems.
Can I drive with Code P0118?
Quick answer: No. Driving with a P0118 code is not advisable.
Driving with a P0118 code should be avoided as the engine could unexpectedly overheat due to incorrect coolant temperature readings, potentially causing severe engine damage. Additionally, the engine may run rich to compensate for perceived temperature issues, which can damage the catalytic converter, which is another expensive repair.
Here’s a more detailed look at driveability with a P0118 code.
| Causes | Can I Drive? | Risks / Safety / Performance |
|---|---|---|
|
Defective Engine Coolant Temperature (ECT) Sensor |
No. Avoid driving with a P0118 code to prevent significant engine and catalytic converter damage. |
Driving with a malfunctioning coolant temperature sensor is extremely dangerous. The engine could severely overheat without warning, potentially leading to catastrophic damage like blown head gaskets, warped cylinder heads, or complete engine failure. |
|
Contaminated Coolant |
No. Avoid driving with a P0118 code to prevent significant engine and catalytic converter damage. |
Contaminated coolant can cause cooling system blockages and reduced heat transfer, leading to severe engine overheating and potential engine failure. |
|
Faulty ECT Sensor Wiring |
No. Avoid driving with a P0118 code to prevent significant engine and catalytic converter damage. |
Faulty wiring can cause incorrect temperature readings, leading the engine to operate at dangerous temperatures without any warning to the driver. This could result in unexpected overheating and severe engine damage. |
|
Defective Engine Control Module (ECM)/Powertrain Control Module (PCM) |
No. Avoid driving with a P0118 code to prevent significant engine and catalytic converter damage. |
A faulty ECM/PCM can cause unpredictable engine behavior and incorrect temperature management, potentially leading to severe engine damage through overheating or improper fuel mixture. The vehicle could also stall unexpectedly while driving, creating a dangerous safety hazard on the road. |
DIY | How To Fix P0118 Causes
Most repairs involving an ECT sensor are best left in the hands of a professional or an advanced DIYer. However, someone with modest skills can tackle replacing contaminated engine coolant, which can trigger a P0118 code in some cases. DIY coolant flush kits are available at auto supplies stores, which makes the task straightforward.
Before tackling any DIY repair, ensure you’re confident about the work ahead. You’ve done your homework and have the correct tools and supplies. Don’t proceed if you’re uncertain about any aspect of the project. The ultimate goal is to avoid injury or causing more damage.
Possible Cause: Contaminated Engine Coolant
What is it?
Clean and fresh antifreeze is essential for an engine’s cooling system. Old or contaminated coolant can cause several problems, including triggering a P0118 code.
How hard is it to fix?
Difficulty Level: Easy/Moderate
Here’s an overview of a basic flush procedure. Always follow the flush kit instructions and the manufacturer’s guidance for coolant type and quantity.
Safety Preparation:
- Park on a flat surface, engine cold (wait 1+ hour)
- Use wheel chocks
- Wear gloves and safety goggles
- Never open a hot radiator cap
- Have coolant catch pan ready
- Work in a well-ventilated area
Required Tools:
- Coolant catch pan
- Flush kit
- New coolant
- Distilled water
- Basic tools for the drain plug
Key Steps:
- Inspect the system for leaks/damaged hoses
- Remove the radiator cap (when cold)
- Drain old coolant by tapping the drain plug
- Flush system with distilled water/flush product
- Run the engine for 10 minutes with the heater on max
- Drain again and clean out the sediment
- Fill with new coolant/water mix
- Bleed air from the system
Important Notes:
- Closely follow the kit instructions to prevent air pockets from developing in the cooling system
- Properly dispose of old coolant (no drains/toilets)
- Clean spills immediately
- Keep pets/children away from coolant
- Follow local disposal regulations
- Check for air bleeder locations
Cost of Repairs
A DIY coolant flush costs about $50–$75, including supplies. Tools are separate.
Other DIY Considerations for Code P0118
We’ve excluded swapping out the ECT sensor as a DIY project because accessing the component requires skill and patience. The sensor can be buried in some vehicles. In addition, the replacement process requires a quick hand to prevent too much coolant from leaking during the parts exchange. Someone with moderate repair skills may be able to handle this project on their own.
Before dealing with any code P0118-related repair, check whether your car is under warranty. You can save money by letting the automaker handle the work. In addition, research if there are any technical service bulletins (TSBs) for your car. TSBs are official repair/correction notices issued by the manufacturer that cover specific problem areas. You can research this online or contact a dealer.
P0118 Code FAQs
What makes and models does code P0118 affect the most?
| Make | Model | Occurrence Frequency |
| Dodge | Grand Caravan | High |
| Buick | Enclave | Medium |
| Chevrolet | Traverse | Medium |
| Chevrolet | Impala | Medium |
| GMC | Yukon | Medium |
| Honda | Pilot | Medium |
What causes a P0118 code?
A P0118 code is triggered when the engine control module (ECM)/powertrain control module (PCM) detects an abnormally high voltage signal from the engine coolant temperature (ECT) sensor circuit. This condition can be caused by a faulty ECT sensor, damaged wiring (open circuit), contaminated coolant, or, in rare cases, a defective ECM itself.
Does P0118 affect Chevy vehicles? What about Nissans?
Yes, P0118 affects both Chevrolet and Nissan vehicles since it’s a generic powertrain code (starts with “P0”) that’s standardized across all manufacturers. Any automobile with an engine coolant temperature sensor can trigger this code when a high voltage condition is detected in the ECT sensor circuit, regardless of the make or model.
FIXD sensor data shows that Chevrolets are the most vulnerable to P0118 codes. Nissans are also susceptible to these problems but to a lesser extent.
References:
Repair-cost estimates, repairpal.com (various dates) and KBB.com. November 19, 2024, from repairpal.com.
Dave Goldberg is an automotive journalist and lifelong car fanatic. He writes for numerous enthusiast and business outlets and is an ongoing contributor to HotCars.com, one of the most popular car culture websites. When he’s not writing or driving, Dave is either under a hood or asleep. His credentials include a BA in Journalism from The George Washington University.
