P0118: Engine Coolant Temperature Sensor Circuit High Input

What does the P0118 error code mean?

The P0118 diagnostic trouble code stands for "Engine Coolant Temperature Sensor Circuit High Input." This code is triggered when the engine control module detects an abnormally high voltage signal from the engine coolant temperature sensor.

If you’re unfamiliar, it’s the engine coolant temperature sensor that monitors the temperature of the engine coolant. The engine coolant temperature also helps the engine control module regulate fuel delivery, ignition timing and cooling fan operation.

Why it's important to address the P0118 error cod

The engine coolant temperature sensor’s accurate performance is critical for optimal engine performance and efficiency. When the engine coolant temperature is inaccurate (or fails), the sensor can cause the engine control module to make incorrect adjustments that lead to overheating, reduced fuel efficiency and increased emissions. If left unaddressed, overheating can cause severe damage to the engine, such as warped cylinder heads or a blown head gasket.

Can I safely drive my car with this error code?

You really shouldn’t drive with the P0118 code. The engine can overheat and cause extensive and expensive damage. The engine control module could also switch to default settings, which leads to poor performance and increased fuel consumption. It's best to address the problem as soon as possible.

Common symptoms associated with the P0118 error code

• Illuminated check engine light
• Engine overheating or running hotter than normal
• Reduced fuel efficiency
• Poor engine performance, such as rough idling or stalling
• Cooling fans running continuously
• Difficulty starting the engine in cold conditions

How to diagnose the P0118 error code

Diagnosing the P0118 code involves these steps:

• Scan for codes: Use an OBD-II scanner to confirm the P0118 code and check for related codes.
• Inspect coolant levels: Check coolant levels and condition to ensure the system is functioning properly.
• Test the engine coolant temperature sensor: Measure the resistance of the engine coolant temperature sensor at different temperatures to ensure it is within the specified range.
• Check wiring and connectors: Look for damaged, corroded, or loose wiring and connectors in the engine coolant temperature sensor circuit.
• Test engine control module input: Verify that the engine control module is receiving accurate voltage signals from the engine coolant temperature sensor.

How to repair the P0118 error code

Repairing the P0118 code typically involves:

• Replacing a faulty engine coolant temperature sensor.
• Repairing or replacing damaged wiring or connectors in the sensor circuit.
• Refilling or flushing the coolant if levels are low or the coolant is contaminated.
• Replacing the thermostat if it is stuck or malfunctioning.
• Clearing the code and test-driving the vehicle to confirm the repair is successful.

Curious about other error codes?

Visit our OBD-II Diagnostic Trouble Codes page to learn more.