P0118: OBD-2 error code interpretation and solutions

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Vehicle engine and/or automatic transmission

Code: P0118 - Engine Coolant Temperature Sensor 1 Circuit High

The P0118 code is a standard OBD-2 diagnostic trouble code indicating that the Engine Control Module (ECM) has detected that the coolant temperature sensor's output signal has exceeded 4.91V or dropped below -40°C. This is common across various car manufacturers, including Renault, Skoda, Nissan, Ford, BMW, Kia, Mercedes, Toyota, Volkswagen, and others.

Causes of OBD P0118

Several main causes could trigger the P0118 fault code on your OBD-II scanner. First, a low coolant level in the engine could be the cause. It can also be caused by a faulty Engine Coolant Temperature (ECT) sensor or issues with the engine coolant thermostat. Occasionally, it happens due to broken or short-circuited wiring at the sensor of the engine coolant temperature sensor. This could also be related to poor connections in the electrical circuit for the ECT sensor.

Symptoms of P0118 Error

There are several signs that a driver may notice or that a mechanic may detect during a test drive. First, the check engine light may come on when the ECM detects a high intake air temperature, exceeding approximately 80°C. Additionally, there may be an issue with starting the engine at low temperatures, which is resolved once the engine warms up. The engine may run unevenly and fluctuate until it warms up, after which it should return to normal operation.

How to Diagnose DTC P0118?

There are several steps that a qualified mechanic should take when attempting to diagnose the P0118 fault code accurately.

Check for damaged or disconnected sensor connectors. They should scan and document the codes from the OBD-II scanner and review freeze frame data to determine when the code was set.
Ensure that the OBD-II fault codes have been cleared and recheck the system to confirm that the code has returned.
Disconnect the sensor connector and check it for corrosion or contact damage, repairing as necessary.
Bridge the two contact pins on the connector to check that the output signal on the scanner exceeds 140°C. If so, this means the wiring is fine, but the coolant temperature sensor should be replaced.
If after replacing the sensor the reading shows more than 140°C, this indicates an open wire, connector issue, or ECM failure, and the mechanic must address this.

How to Avoid Common Mistakes with OBD P0118 Code?

If you follow the steps above for diagnosis and repair, you should not face problems when fixing the vehicle and resolving the code. However, here are some common mistakes made when addressing this fault code:

Not visually inspecting the problem area before beginning work.
Skipping steps in the manufacturer's testing procedure.
Replacing the ECT sensor without clearly identifying the problem.
Not connecting and verifying ECM data to check if the new ECT sensor's output temperature aligns with expectations.

How Serious is P0118 Error?

The P0118 code causes the engine to enter limp mode, which can result in rough or fluctuating engine performance until the engine warms up to the optimal temperature.

This limp mode can also lead to increased fuel consumption, carbon build-up on engine components, and various issues during operation. This depends on the manufacturer’s limp mode strategy. Prolonged driving in limp mode may require additional repairs to remove excessive carbon deposits.

This could also lead to potential ignition issues in the future and cause the cooling fans to run continuously while the engine is running.

How to Fix P0118 Code?

There are several standard and simple fixes that can resolve this fault code:

Repair or replace the ECT connector.
Repair or replace any damaged wiring as necessary.
Replace the ECT sensor with a new one.

Conclusion

Although the DTC P0118 does not result in a complete vehicle failure, it affects optimal performance. Without proper diagnosis and repair, this issue can lead to further, more costly repairs and maintenance for the vehicle.

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OBD P0118 code analysis and solutions

The page presents a in-depth analysis of code P0118 for Opel, Renault, VW (Volkswagen), Ford, Peugeot, Mitsubishi, Skoda, BMW, Citroën, Toyota, Lada, Honda, Kia, and other models to investigate probable causes and solutions related to OBD-II errors, with emphasis on the issue. We provide engineering documentation and approaches for diagnostics to identify and find a solution effectively. Our resource is designed to be a comprehensive source of information on OBD 2 errors, providing you with the necessary tools for successful repair and maintenance of auto. If during the repair of OBD2 errors you need to purchase parts, don’t forget to visit Avtopro!