Error P0117 – how to fix it?

Code definition P0117

Problem with the low output signal from the engine coolant temperature (ECT) sensor.

What does code P0117 mean.

P0117 is a generic OBD-II code that indicates that the engine control module (ECM) has noticed that the ECT sensor output is less than 0.14 volts or greater than 140°C (284°F).

What causes code P0117?

The ECT sensor input to the ECM has exceeded 0.14 V or 140°C (284°F), indicating a short in the sensor or wiring.

The ECT sensor or wiring is shorted.

What are the symptoms of code P0117?

• The ECM turns on the engine control light and enters safety mode by overriding the 176°F input.
• The engine may have difficulty starting when the engine is cold.
• The engine may run unevenly and hesitate until it warms up.
• The engine should run almost normally after warming up.

Note: Symptoms are determined by the manufacturer’s ECM safety strategy for the vehicle during malfunction and may vary by manufacturer and vehicle.

How does a mechanic diagnose the P0117 code?

• Visual inspection for problems with electrical connectors, wiring or sensors.
• The technician scans and documents the codes received and reviews the freeze frame data to see when the code was set.
• The codes must be reset to clear the OBD-II error codes and retest the vehicle to see if the code has returned.
• Disconnect the ECT sensor, watch the live data to see if the readings change from over 284°F to -40°F.
• If the readings drop to -40°F, then replace the ECT sensor, if not, look for a shorted harness, connector or ECM.

Most common errors when diagnosing the P0117 code.

• Do not perform these simple steps:
• Always perform a visual inspection first.
• Follow the manufacturer’s test procedure step by step, without skipping any steps.
• Do not replace the ECT sensor unless testing indicates a problem.
• Before installing a new ECT sensor, try turning it on and look at the ECM data to see if the sensor’s output temperature is as expected.

How serious is the code P0117?

• The P0117 code will cause the engine ECM to enter a fail-safe mode.
• The failsafe mode may cause the engine to run poorly and float until the engine warms up to operating temperature.
• Electric cooling fans may run continuously.

What repairs can repair code P0117?

1. Reset the trouble codes and perform a road test.
2. Repair or replace the ECT connector
3. Repair or replace wiring if necessary
4. Replace ECT with new sensor

Additional notes on code P0117

1. Short-circuiting the ECT sensor is the most common fault.
2. Some faults for code P0117 other than the sensor include a short in the harness or a corrosion problem in the connector.