Error P0118 – how to fix?

Code definition P0118

Engine Coolant Temperature (ECT) Sensor Circuit High Open Problem.

What does the code P0118 mean

P0118 is a general OBD-II code indicating that the engine control module (ECM) observed a voltage rise above 4.91V or below -40 ° C (-40 ° F) at the ECT sensor output.

What causes the P0118 code?

The ECT sensor range on input to the ECM was 4.91 or less than -40 degrees F, indicating an open circuit in the sensor, connector, or wiring harness.

What are the symptoms of the P0118 code?

• The ECM turns on the check engine light and goes into safety mode, replacing the 176 degrees F input.
• The engine may have difficulty starting when cold, and start normally when warm.
• Engine may run jerky and hesitate until warm.
• The engine should run almost normally after warm up.

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

How does the mechanic diagnose the P0118 code?

• Checks for disconnected or damaged sensor connectors.
• Scan and document received codes, and view data from frozen frames to see when a code was set.
• Clear the OBD-II error codes and retest the system to see if the code has returned.
• Disconnect the sensor connector and inspect for corrosion or bent pins and repair as needed.
• Connect the two pins of the connector to see if the output on the scanner shows more than 284 degrees F, indicating the wiring is fine, and replace the ECT sensor.
• Above 284 degrees F, the circuit has an open circuit in the wiring, connector, or ECM and will be repaired by a technician.

The most common errors when diagnosing the P0118 code

• Do not visually check the problem area first.
• Failure to follow the manufacturer’s test procedure step by step and skipping steps.
• Replacing the ECT sensor without knowing for sure what the problem is
• Without plugging it in and looking at the ECM data to see if the sensor temperature output is as expected before installing a new ECT sensor.

How serious is the P0118 code?

Code P0118 will cause the engine ECM to enter fail-safe mode, which may cause the engine to run sluggishly or to hesitate until the engine is warmed up to operating temperature. Fail-safe operation can also cause excessive fuel consumption, carbon build-up on engine components, and a variety of driving ailments, depending on the manufacturer’s fail-safe strategy. Driving the vehicle with the vehicle in emergency mode for an extended period of time may require additional repairs to remove carbon build-up or to correct any ignition problems. In addition, the electric cooling fans can run continuously while the engine is running.

What repairs can fix the code P0118?

1. Repair or replacement of the ECT connector
2. Repair or replace the open circuit in the wiring harness as needed.
3. Replace the ECT sensor with a new one.

Additional considerations about the P0118 code

Most of the faults for P0118 involve an ECT sensor open circuit fault.