P0118
High SeverityEngine Coolant Temperature Sensor Circuit High
Cooling System
P0118 — Instant Answer
Engine Coolant Temperature Sensor Circuit High
Severity: HIGH SEVERITY
Meaning: ECT sensor voltage is above maximum, reading as extremely cold. Usually an open sensor circuit.
Safe to drive? NO if CEL is flashing. YES with caution if solid, but repair this week.
Estimated repair cost: $10 - $25
Most common causes:
- 1. Open circuit ECT sensor (35-45% of cases)
- 2. Disconnected sensor connector (35-45% of cases)
- 3. Broken wire (10-25% of cases)
Symptoms
- ⚠️Fans never turning on
- ⚠️Rich running when cold
- ⚠️Poor cold-start idle
- ⚠️Check engine light
Related Symptoms
Common Causes
How to Diagnose P0118
- 1Check ECT connector is plugged in
- 2Measure sensor resistance
- 3Check wiring continuity
- 4Replace sensor if open
OEM Procedures for P0118
Engine Coolant Temperature Circuit High Input Found 11 OEM service manual procedures.
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Coolant Temperature Sensor - Removal & Installation
Showing 8 of 11 procedures
OEM Diagnostic Flowchart
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Parts & Tools for This Job
Common parts shoppers buy for P0118 Engine Coolant Temperature Sensor Circuit High.
Thermostat
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Engine Coolant
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Radiator
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Water Pump
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Coolant Temp Sensor
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OBD2 scanner
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Check SpecificationsBattery tester
Check cranking and charging health before replacing expensive parts.
A weak battery can mimic alternator or starter problems.
Check SpecificationsMultimeter kit
Confirm voltage, continuity, and sensor power with one simple kit.
A meter is the cheapest way to rule out a bad circuit fast.
Check SpecificationsRelated Resources
Repair guides, symptom pages, and wiring diagrams related to P0118.
OEM Manual Evidence
Browse →PGM-FI DTCS — 2013 Acura MDX 3.7L Eng VIN 2 Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowledge Reimagined Home >> Acura >> 2013...
PGM-FI DTCS — 2013 Acura MDX 3.7L Eng VIN YD2 Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowledge Reimagined Home >> Acura >> 20...
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Engine Control System DTCS — 2013 Acura RDX 3.5L Eng VIN 3 Service Manual ~ LEMON Manuals LEMON Manuals: Repair Knowledge Reimagined Home >...
Related Symptoms
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Related Codes
The ECT sensor circuit has a general malfunction. This sensor tells the ECM how warm the engine is for fuel, timing, and fan control.
ECT sensor voltage is too low, indicating an impossibly high temperature. Usually a shorted sensor.
The ECT sensor reading is not changing as expected during warm-up. Either the sensor is lazy or the thermostat is preventing normal warm-up.
Frequently Asked Questions
- Will P0118 prevent fans from running?
- Yes — the ECM thinks the engine is cold, so it will not activate the cooling fans. This can lead to actual overheating. Fix immediately.
- Is P0118 dangerous?
- Potentially yes — if the fans do not run, the engine can overheat in traffic. Fix right away.
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Author & Review
Published by AllOEMManuals, founded by Lyndon Bedford, an automotive technician with 20 years of experience. He owned and operated a mechanic shop in Hurst, Texas from 2014 to 2022 and continues hands-on repair work.
Content may combine manual references, general repair templates, and AI-assisted drafting. Confirm the source, vehicle configuration, and applicability before working. Report corrections through our contact page.
Last updated: 2026-10-29