How much does it cost to fix P0117?

DIY repair typically costs $10–$40 for parts. Professional repair runs $100–$300 including parts and labor.

P0117

Powertrain

Moderate

Engine Coolant Temperature Sensor 1 Circuit Low Input

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The P0117 code indicates that the voltage signal from your Engine Coolant Temperature (ECT) sensor is below the normal operating range. In most ECT circuits, lower voltage corresponds to higher temperature — so this code essentially means the ECM is seeing a signal that suggests the coolant is impossibly hot, typically well above the normal 195–220°F operating range.

The most common cause is a failed ECT sensor with an internal short circuit. The sensor is a simple and inexpensive part, usually located near the thermostat housing or on the engine block. Wiring problems — such as chafed insulation causing a short to ground — are the second most likely cause. When this code is active, the ECM enters a failsafe mode that can cause the cooling fans to run nonstop and the engine to run poorly until it warms up.

This is generally an easy and affordable DIY repair. An ECT sensor typically costs $10–$30 and takes about 15–30 minutes to replace. Before replacing the sensor, check the wiring and connector for obvious damage or corrosion. If you notice the cooling fans running constantly from a cold start, or your temperature gauge is pegged at maximum, the P0117 code is very likely active. Address it within a week to avoid poor fuel economy and unnecessary wear on your cooling fans.

Severity

Moderate — Address SoonThis Week

Symptoms

•Check Engine Light illuminated
•Engine runs rough or hesitates, especially when cold
•Electric cooling fans may run continuously even when engine is cold
•Poor fuel economy
•Temperature gauge reads maximum or behaves erratically

Likely Causes

Shorted ECT sensor (internal short circuit)40%

The ECT sensor uses a thermistor that changes resistance with temperature. An internal short drives the resistance abnormally low, making the ECM interpret an extremely high temperature.

Short circuit in wiring harness to ECT sensor25%

Damaged insulation or pinched wires in the ECT circuit can cause the signal wire to short to ground, sending a low-voltage signal that mimics an extremely hot reading.

Corroded or water-damaged ECT sensor connector20%

Moisture intrusion or corrosion at the connector creates unintended electrical paths that lower the circuit resistance, producing a false low-input signal.

Faulty Engine Control Module (ECM)15%

In rare cases, the ECM's internal pull-up resistor or analog-to-digital converter for the ECT input can fail, reading low voltage regardless of sensor condition.