P0118 on Chevrolet
Engine Coolant Temperature Sensor Circuit High
P0118 on Chevrolet vehicles indicates engine coolant temperature sensor circuit high. Au7o has documented this code across 1 Chevrolet model — most commonly on Cobalt. 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 Chevrolet range from $150 to $600, 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 Chevrolet by Model
Chevrolet Cobalt(1 issue)
- Ecotec Thermostat Housing and Water Pump Coolant Leak — Slow Loss with No Visible Puddle2005-2010
On the 2.2L/2.4L Ecotec the thermostat is integrated into a plastic housing on the back side of the engine facing the firewall, and the water pump sits behind the timing cover on the passenger side. Both are recurring leak points. The rear thermostat housing seal hardens and the housing itself corrodes and seeps, and because the leak is tucked against the firewall the coolant evaporates on the hot block instead of dripping — so owners chase a steadily dropping reservoir with no puddle in the driveway, a complaint that appears over and over on the Cobalt forums. The water pump leaks at its gasket toward the passenger side, and because it is timing-chain driven, a leaking pump can wash the front of the engine and contaminate the chain area. A slow leak that runs the car low leads to overheating and, on the Ecotec, a warped or cracked head.
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What does P0118 mean on Chevrolet?▼
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 Chevrolet specifically, this code is documented across 1 model.
What causes P0118 on Chevrolet vehicles?▼
Common causes on Chevrolet: 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 Chevrolet?▼
Repair costs on Chevrolet range from $150 to $600, depending on the specific model and root cause.
Which Chevrolet models have P0118 documented?▼
Au7o has documented P0118 on 1 Chevrolet model: Cobalt.