P0118 on GMC
Engine Coolant Temperature Sensor Circuit High
P0118 on GMC vehicles indicates engine coolant temperature sensor circuit high. Au7o has documented this code across 1 GMC model — most commonly on Yukon. P0118 indicates the engine coolant temperature (ECT) sensor circuit is reading abnormally high voltage, which the computer interprets as an implausibly cold coolant temperature. The ECT sensor changes resistance with temperature and tells the PCM how hot the engine is so it can manage fuel, the cooling fans, and the gauge. High voltage on this circuit usually points to an open circuit or a sensor reporting an unrealistically low temperature. The car may run rich, struggle to enter closed-loop operation, idle poorly, or show an inaccurate temperature gauge. Typical repair costs on GMC range from $120 to $450, depending on the specific model and root cause.
Common Causes of P0118
- •Faulty (open) engine coolant temperature sensor
- •Open or broken wire in the ECT signal circuit
- •Loose, corroded, or disconnected sensor connector
- •Poor ground or open in the sensor return circuit
- •Damaged wiring harness near the sensor
- •Corrosion in the connector terminals
- •Failed PCM input (rare)
P0118 on GMC by Model
GMC Yukon(1 issue)
- Engine Overheat/Fail-Safe Mode from Thermostat and Coolant Temp Sensor2015-2019
A worn or leaking factory thermostat that stays open (plus a failing engine coolant temperature sensor) prevents the engine from reaching normal operating temperature. The ECM interprets the low/erratic reading as a sensor fault and enters a protective fail-safe mode: the electric cooling fans run at full speed continuously, the temperature gauge may drop to zero or read erratically, the A/C compressor may be disabled, and fuel economy suffers. It is a common and well-documented complaint across 2015-2019 5.3L/6.2L trucks and SUVs.
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What does P0118 mean on GMC?▼
P0118 stands for "Engine Coolant Temperature Sensor Circuit High." P0118 indicates the engine coolant temperature (ECT) sensor circuit is reading abnormally high voltage, which the computer interprets as an implausibly cold coolant temperature. The ECT sensor changes resistance with temperature and tells the PCM how hot the engine is so it can manage fuel, the cooling fans, and the gauge. High voltage on this circuit usually points to an open circuit or a sensor reporting an unrealistically low temperature. The car may run rich, struggle to enter closed-loop operation, idle poorly, or show an inaccurate temperature gauge. On GMC specifically, this code is documented across 1 model.
What causes P0118 on GMC vehicles?▼
Common causes on GMC: Faulty (open) engine coolant temperature sensor, Open or broken wire in the ECT signal circuit, Loose, corroded, or disconnected sensor connector, Poor ground or open in the sensor return circuit, Damaged wiring harness near the sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0118 on a GMC?▼
Repair costs on GMC range from $120 to $450, depending on the specific model and root cause.
Which GMC models have P0118 documented?▼
Au7o has documented P0118 on 1 GMC model: Yukon.