OBD-II Trouble Codes

P0117 Code: Engine Coolant Temperature Sensor 1 Circuit Low

Reading Time: 3 minutes

Proper engine temperature must be maintained for the engine to function well. If the engine runs cold, it can consume excessive amounts of fuel, affecting the overall performance of the vehicle. If the engine runs too hot, it can permanently damage your engine and its surrounding components.

The engine cooling system maintains the optimal operating temperature of an engine. The engine coolant absorbs heat from the engine, while the sensors monitor its temperature. The P0117 code indicates a problem with one of the engine coolant temperature sensors in your vehicle. Find out more about this error code and what to do in case you encounter it using this short guide.

engine coolant temperature sensor
The P0117 code indicates a problem with one of the engine coolant temperature sensors in your vehicle.

What Does the P0117 Code Mean?

Diagnostic trouble code (DTC) P0117 stands for “Engine Coolant Temperature Sensor 1 Circuit Low.” It indicates that the vehicle’s powertrain control module or PCM has detected a low voltage input from the engine coolant temperature (ECT) sensor 1.

The ECT sensor is a thermistor, which is a kind of resistor that monitors temperature. The ECT sensor changes resistance as the temperature of the coolant it’s in contact with changes. This means that if the engine is cold, the resistance and voltage goes up. Alternatively, if the engine is hot, the resistance and the voltage goes down.

The ECT sensor monitors these changes in the temperature of your engine’s coolant. The information it obtains is sent to the PCM, which uses the data to regulate the air-to-fuel ratio, cooling fan operation, ignition spark timing, and other powertrain-related outputs.

Once the PCM detects a signal voltage that’s lower than the normal operating range of the sensor, the OBD code P0117 registers in your vehicle’s memory. The low signal that the PCM detects from the ECT sensor can mean that the engine coolant is excessively hot.

Note: The definition of code P0117 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0117 Code?

There are a lot of issues that could trigger the engine code P0117. Below are just some of the possible causes of P0117:

What are the Common Symptoms of the P0117 Code?

Should you encounter the P0117 code, there are a few signs you have to look out for. This code points to issues with the ECT sensor and high engine coolant temperature. Below is a list of the most common symptoms of this trouble code:

How to Diagnose the P0117 Code

Like other OBD-II codes, the P0117 code has multiple possible causes. It’s important to pinpoint the exact reason behind the issue to determine a proper fix. Here are some video resources that can help you reach an accurate diagnosis:

How to Fix the P0117 Code

There is no single solution to the P0117 code because there are a lot of reasons why this code is set. Repair steps will also vary depending on the vehicle’s make and model. That’s why proper diagnosis is important.

If you’re trying to resolve the issue yourself, you’ll need several trusted resources that can give you accurate information on repairs and diagnosis. Repair guides and manuals that contain factory repair information, like ALLDATA, will give you step-by-step instructions on how to address the problem. Consider getting an ALLDATA subscription to expand your knowledge base on OBD-II diagnosis and repair.

coolant temperature sensor connector
Repair steps will also vary depending on the vehicle’s make and model. That’s why proper diagnosis is important.

Other Notes About P0117

Most of the symptoms of the P0117 code indicate performance issues with the engine. This means it must be resolved immediately. P0117 can put the vehicle in a failsafe mode, which causes the car to be relegated to a certain speed and/or gear range.

Address the issue immediately. Stop driving the vehicle and go to a shop as soon as the code registers or a combination of its symptoms appear. Ignoring this trouble code may lead to further damage to your engine and your vehicle.

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