Chevy Check Engine Code
P0118 on Chevy
Engine Coolant Temperature Sensor Circuit High Input
Also covers: Chevrolet, GMC, Buick, Cadillac, GM
P0118 on Chevy: what makes it different
Many Chevy trucks and SUVs built on the Vortec V8 platform use a single-wire ECT sensor threaded into the thermostat housing or cylinder head, with a connector exposed to engine bay moisture and road splash — a design that's prone to corrosion-related high-resistance faults that trigger P0118.
Most-affected engines
- Vortec 4.8L/5.3L/6.0L V8 (Silverado, Tahoe, Suburban)
- Ecotec 2.2L/2.4L (Cobalt, Malibu, Equinox)
Common model years: 1999–2013 (Vortec trucks), 2005–2013 (Ecotec)
Most likely cause on Chevy
Corroded or loose ECT sensor connector causing the circuit to read an abnormally high voltage (interpreted as extremely cold coolant).
Known Chevy engine-family issues
GM's single-wire ECT sensor and connector design on Vortec-equipped trucks is a known weak point for corrosion over time, especially in vehicles regularly exposed to road salt or moisture intrusion in the engine bay.
Chevy-specific causes (most common first)
- Corroded or oxidized ECT sensor connector pins (common on high-mileage Vortec trucks exposed to moisture)
- Failed ECT sensor with an open or drifting internal resistance
- Wiring harness insulation rubbed through near the exhaust manifold or valve cover
- Coolant seepage into the sensor connector from a weeping housing gasket
- Corrosion at the PCM-side wiring connector
- Low coolant level exposing the sensor tip intermittently
Chevy-specific diagnostic tip
Back-probe the ECT sensor connector and compare its live voltage/temperature reading on a scan tool against the Intake Air Temperature (IAT) sensor at a cold start — they should read within a few degrees of each other; a big mismatch points to the ECT circuit rather than actual coolant temperature.
Symptoms drivers report
- Check engine light
- Cold-start hard / no-start
- Cooling fans running at low temp
- Erratic gauge
Typical repair cost on Chevy
Most Chevy owners fix P0118 for between $80 and $220, depending on which underlying cause turns out to be at fault. Start with the most-likely cause for your vehicle — Corroded or loose ECT sensor connector causing the circuit to read an abnormally high voltage (interpreted as extremely cold coolant). — before throwing parts at it.
Chevy P0118 FAQ
Why does P0118 show up so often on GM Vortec trucks?
The ECT sensor connector sits low in the engine bay near coolant passages and is exposed to road splash, making corrosion a common cause of a high-resistance (high voltage) fault over time.
Can I drive with P0118 on my Silverado or Tahoe?
Short term yes, but the PCM may default to a fixed fuel/timing strategy assuming the engine is cold, which can hurt fuel economy and cold-start drivability until it's fixed.
Does replacing the ECT sensor always fix P0118 on Chevy trucks?
Not always — check the connector and wiring for corrosion first, since a clean connector repair often resolves the code without needing a new sensor.
Related codes
Drive a different make? See the general P0118 guide for cross-vehicle causes and symptoms.
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