P0118
Fix within a few daysThe engine computer (PCM) detects a voltage from the Engine Coolant Temperature (ECT) sensor that is too high, indicating an extremely cold temperature or an open circuit in the sensor's wiring.
Code P0118 means your engine's computer sees a high signal from the coolant temperature sensor. Common causes: Faulty ECT sensor (70%), wiring issues (25%). Drivability: Yes, but fix soon. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0118?
Yes, for short trips only
Essential trips under 10 miles, avoid highways. Fix within a few days to prevent further damage.
Stop driving immediately if: Flashing CEL, significant power loss, or engine overheating (though unlikely with this specific code)
Symptoms of P0118
- 1Check Engine Light illuminated
- 2Engine running rich (strong fuel smell, black smoke from exhaust)
- 3Poor fuel economy
- 4Hard starting, especially when the engine is cold
- 5Engine fan running constantly (even when the engine is cold)
- 6Rough idle
Common Causes of P0118
Parts most likely causing this code, ranked by probability
The sensor itself fails internally, sending an incorrect high voltage signal to the PCM, which interprets it as an extremely cold temperature or an open circuit.
70% of P0118 cases are fixed by replacing this part
An open circuit, corrosion, or damaged wires in the ECT sensor's harness or connector prevents the correct signal from reaching the PCM.
25% of P0118 cases are fixed by repairing or replacing wiring/connector
A rare internal fault within the PCM can cause it to misinterpret the ECT sensor signal or fail to process the circuit correctly.
5% of P0118 cases are fixed by replacing the PCM
Check These First (Before Buying Parts)
- Visually inspect the ECT sensor connector for corrosion or damage.
- Check your engine's coolant level; ensure it is full and there are no air bubbles.
How to Diagnose P0118
- 1Visually inspect the ECT sensor and its connector for any signs of damage, corrosion, or loose connections.
- 2Check the coolant level; ensure it is full and there are no air pockets around the sensor.
- 3Using a multimeter, test the resistance of the ECT sensor at various temperatures (if possible) and compare it to manufacturer specifications.
- 4With the ignition off, disconnect the ECT sensor and check for continuity in the wiring harness between the sensor connector and the PCM connector.
- 5Use a scan tool to monitor the ECT sensor's live data; look for erratic readings or a constant extremely low temperature reading.
P0118 on Popular Vehicles
Honda Accord
2003-2024ECT sensor failure is common. The sensor is typically located on the cylinder head or thermostat housing. Inspect the wiring harness for rodent damage or corrosion.
75% fixed by replacing ECT sensor
Toyota Camry
2007-2024ECT sensor issues are known. Sometimes, a low coolant level or air pocket can cause erratic readings leading to this code, though the primary cause is usually the sensor itself or its wiring.
70% fixed by replacing ECT sensor
Ford F-150
2004-2024Wiring harness issues, especially near the sensor, can be a factor due to engine bay heat and vibration. Always check the connector and harness thoroughly before replacing the sensor.
60% fixed by replacing ECT sensor
Frequently Asked Questions
What does P0118 mean?
P0118 indicates that the Engine Coolant Temperature (ECT) sensor circuit is sending a voltage signal that is too high to the Powertrain Control Module (PCM). This typically means the PCM is reading an extremely cold engine temperature or detecting an open circuit.
Can I drive with P0118?
Yes, you can drive with P0118, but you must fix it within a few days. The engine will run rich, which wastes fuel and can damage your catalytic converter over time. The engine fan might also run constantly.
Will P0118 clear itself?
No, P0118 will not clear itself. The underlying electrical fault or sensor failure must be repaired. Once the repair is made, you will need to clear the code with an OBD-II scan tool.
How do I fix P0118 myself?
Start by inspecting the ECT sensor and its wiring for visible damage or corrosion. If the wiring looks good, test the sensor's resistance with a multimeter. If the sensor is faulty, replace it. This often involves draining a small amount of coolant, unscrewing the old sensor, and installing a new one.
How much does it cost to fix P0118?
The cost to fix P0118 yourself is typically $20-$80 for a new ECT sensor. If you take it to a shop, expect to pay $150-$500, which includes parts and labor.
P0118 keeps coming back - why?
If P0118 keeps returning, it indicates the initial repair did not address the root cause. This often points to a persistent wiring issue, a faulty connector, or a rare PCM problem that was overlooked. Ensure all connections are clean and secure, and consider a thorough wiring harness inspection.
Will P0118 fail emissions/smog test?
Yes, P0118 will cause your vehicle to fail an emissions or smog test. The Check Engine Light will be illuminated, and the engine running rich will result in higher-than-acceptable emissions.
What's the difference between P0118 and P0117?
P0118 indicates a 'high input' from the ECT sensor, meaning the PCM sees a voltage that's too high (suggesting an open circuit or extremely cold temperature). P0117 indicates a 'low input,' meaning the PCM sees a voltage that's too low (suggesting a short circuit or extremely hot temperature).
P0118 on Honda Accord
P0118 is a common code on Honda Accords, especially older models. The ECT sensor itself is a frequent failure point. Replacing the sensor, often located near the thermostat housing or on the cylinder head, usually resolves the issue. Always check the connector for corrosion first.
Questions to Ask Your Mechanic
Did you test the resistance of the ECT sensor at different temperatures?
Good answer: Yes, I compared the sensor's resistance readings to the manufacturer's specifications at ambient temperature and after warming up the engine. It was out of spec.
What did you find when checking the wiring continuity between the ECT sensor and the PCM?
Good answer: I found an open circuit in the signal wire, or I confirmed full continuity, ruling out a wiring issue.
Repair Cost Estimate
DIY Repair
Parts only
$20-$80
Shop Repair
Parts + labor
$150-$500
Save $130-$420 by doing it yourself
Difficulty
beginner
Time
0.5-1.5 hours
Beginner-friendly - replacing the ECT sensor is typically a simple task requiring basic hand tools and minimal mechanical experience.
Cost of Waiting
Ignoring P0118 means your engine runs rich, which will foul spark plugs, contaminate your engine oil, and severely damage your catalytic converter. A $50 sensor fix now prevents a $1,200-$2,500 catalytic converter replacement later.
While You're In There...
If the ECT sensor is located near the thermostat, it makes sense to replace the thermostat if it's old or has never been replaced, as you're already draining some coolant and accessing the area.
Since you may need to drain some coolant to replace the sensor, it's a good opportunity to perform a coolant flush and refill with fresh coolant, especially if it's due for maintenance.
Tools You'll Need
- OBD-II Scan Tool
- Multimeter
- Socket set
- Wrench set
- Pliers
- Coolant drain pan
P0118 is a common sensor code that usually points to a straightforward electrical issue. Most repairs are under $80 for parts and your engine will run much more efficiently afterward.
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Your Next Steps
Step 1: Visually inspect the ECT sensor and its electrical connector for any obvious damage, corrosion, or loose wires. Ensure the coolant level is full.
Step 2: If the visual inspection doesn't reveal the issue, use a multimeter to test the resistance of the ECT sensor. Compare your readings to the manufacturer's specifications for your vehicle.
Step 3: If the sensor tests faulty, replace the Engine Coolant Temperature sensor. You'll likely need a new sensor and possibly a small amount of fresh coolant.