Definition of the code P0118
Problem with the high degree of opening of the engine coolant temperature (ECT) sensor circuit.
What code P0118 means.
P0118 is a generic OBD-II code that indicates that the engine control module (ECM) has observed a voltage rise above 4.91V or below -40°C (-40°F) at the output of the ECT sensor.
What causes code P0118?
The ECT sensor range at the ECM input was 4.91 or less than -40 degrees F, indicating an open circuit in the sensor, connector or wiring.
What are the symptoms of the P0118 code?
- The ECM turns on the check engine light and goes into safe mode, overriding the 176 degree F input.
- The engine may have difficulty starting when cold and starts normally when warmed up.
- The engine may run erratically 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 P0118 code?
- He checks to see if the sensor connectors are disconnected or damaged.
- It scans incoming document codes and reviews the frozen frame data to see when a code has been set.
- Clear the OBD-II error codes and retest the system to see if the code came back.
- Disconnect the sensor connector and check for corrosion or bent contacts, and repair if necessary.
- Connect the two pins of the connector to see if the output on the scanner shows more than 284 degrees F, indicating that the wiring is OK, 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.
Most common errors when diagnosing the P0118 code
- Failed to visually inspect the problem area first.
- Failing to follow the manufacturer’s step-by-step test procedure and skipping steps.
- Replacing an ECT sensor without knowing for sure what the problem is
- Not plugging it in and looking at the ECM data to see if the sensor output temperature is as expected before installing a new ECT sensor.
How serious is the code P0118?
The P0118 code will cause the engine ECM to enter a fail-safe mode, which can cause the engine to run poorly or hesitate until the engine warms up to operating temperature. Failsafe mode can also cause excessive fuel consumption, carbon deposits on engine components, and various driving ailments, depending on the manufacturer’s failsafe mode strategy. Driving the vehicle for a long period of time with the vehicle in fail-safe mode may require additional repairs to remove carbon buildup or repair any ignition problems. In addition, the electric cooling fans may run continuously while the engine is running.
What fixes can repair a P0118 code?
- ECT connector repair or replacement
- Repair or replace the open circuit in the wiring harness, if necessary.
- Replacement of the ECT sensor with a new one.
Additional notes to consider about code P0118
Most faults for code P0118 involve an open circuit failure of the ECT sensor.
