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P0118 is a diagnostic trouble code (DTC) for "Engine Coolant Temperature (ECT) Sensor Circuit High Open Problem". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
Engine Coolant Temperature (ECT) sensor circuit high open problem
P0118 is the OBD-II generic code that indicates the Engine Control Module (ECM) has seen the ECT sensor output go more than 4.91 V or less than -40°C (-40°F).
The ECT sensor range input to the ECM went to 4.91 or less than -40 deg F indicating an open circuit in the sensor, connector or wiring.
The ECM turns the Check Engine Light on and goes into failsafe mode, substituting input to 176 deg F.
The engine may have a hard start when engine is cold, and start normal when warm.
The engine may run rough and hesitate until the engine warms up.
The engine should run close to normal once the engine warms up.
Note: The symptoms are determined by the manufacturer failsafe ECM strategy for the vehicle during a failure and may vary between manufacturers and vehicles.
Inspects for disconnected sensor connectors or damaged connectors
Scans and documents the codes received and views the freeze frame data to see when the code was set
Clears the OBD-II fault codes and retests the system to see if the code comes back
Disconnects the sensor connector and inspects for corrosion or bent pins and repairs as needed.
Connects the two connector pins together to see if the output on scanner shows above 284 deg F, indicating the wiring is okay, and replaces the ECT sensor
Above 284 deg F, the circuit has an open circuit in the wiring, connector or ECM and will be fixed by the technician
Not visually inspecting the problem area first
Not following the manufacturer's pinpoint test procedure step-by-step, and skipping steps
Replacing the ECT sensor without knowing for sure that it is the problem
Not connecting it and viewing the ECM data to see if the temperature output from the sensor is as expected before installation of the new ECT sensor
The P0118 code will put the engine ECM to go into a failsafe mode, which may cause the engine to run rough, or hesitate until the engine warms up to operating temperature. The failsafe mode may also cause excessive fuel consumption, carbon fouling of engine components, and various drive complaints, depending on the manufacturer's failsafe mode strategy. Driving a vehicle for an extended time with the vehicle in failsafe mode may require additional repairs to remove carbon, or repair possible ignition problems. Also, electrical cooling fans may run continuously while the engine is running.
Most failures for code P0118 involve ECT sensor open circuit failure.
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