OBD-II Code · Sensors
P0118
ECT Sensor Circuit High Input
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$75–$200
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
ECT reading too hot (but engine may be fine).
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Engine going into limp mode
- Temp gauge pegged
Likely causes
- Failed sensorMost common
- Wiring open circuit
Read the full diagnostic procedureP0118 is the opposite failure: ECT signal is pinned high (typically above about 4.9 V), which the PCM interprets as impossibly cold (often -40 F show…
P0118 is the opposite failure
ECT signal is pinned high (typically above about 4.9 V), which the PCM interprets as impossibly cold (often -40 F shown on the scan tool). Cheapest-first: jump the signal pin to the sensor-ground pin at the harness connector with the key on. The PCM should now report a very hot coolant reading (roughly 250 F or pinned). If it does, the sensor is open internally or has lost its ground reference; replace the sensor first. If jumping the pins produces no change, the open is in the signal wire, the ground wire, or the PCM input. Verify the sensor ground has continuity to PCM ground (under 0.1 ohm). A healthy ECT should read about 2.5 to 3.0 V at 70 F and 0.5 to 1.0 V at 200 F; an open sensor reads pinned at the 5 V reference. Caveat: a corroded ground splice can present exactly like an open sensor, so always verify the ground path before throwing parts at it.
Vehicle-specific patterns1999-2007 GM 4.8/5.3/6.0 trucks routinely throw P0118 from the under-intake harness corrosion eating the ECT ground splice (S211/S212 area).
- 1999-2007GM 4.8/5.3/6.0 trucks routinely throw P0118 from the under-intake harness corrosion eating the ECT ground splice (S211/S212 area).
- 2005-2010Chrysler 300/Charger 5.7 Hemi has the ECT connector terminal back-out problem at the thermostat housing.
- 2003-2008Toyota Tundra/4Runner 4.7L 2UZ-FE has cracked sensor housings that go open-circuit after heat-cycling.
- 2007-2013BMW N52/N54 cylinder-head temperature sensors fail open as a wear item around 80k-100k miles.
Estimated repair$40 to $280.
Look up another code
P0118 — frequently asked
What does a P0118 code mean?
ECT reading too hot (but engine may be fine).
What causes a P0118 code?
Common causes: Failed sensor; Wiring open circuit.
What are the symptoms of a P0118 code?
Typical symptoms: Check engine light; Engine going into limp mode; Temp gauge pegged.
Is it safe to drive with a P0118 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $75-$200.
How do I diagnose a P0118 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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