Causes and Fixes P0118 Code Honda

By | March 11, 2024

Causes and Fixes P0118 Code Honda
If you have a Honda with a P0118 error code, there is a problem with a coolant heat sensor.

The official definition is an “Engine Coolant Temperature Sensor 1 Circuit High.”

There can be 2-4 engine coolant temperature sensors (ECT) in a Honda, depending on the year and model.

What is a P0118 Code Honda Error Code?

A Honda with a P0118 OBDII Code is an “Engine Coolant Temperature Sensor 1 Circuit High.”

The coolant sensor is what’s called a Thermistor, which is a resistor whose resistance changes with temperature.

The onboard computer (ECM/PCM) sends out 5 volts to the coolant sensor, which will have a voltage drop as the engine heats up.

If the sensor does not have a voltage drop and stays at 5 volts, the ECM/PCM reports the code P0118.

This usually means that a sensor has malfunctioned or has an open circuit.

Honda Engine Coolant Temperature Sensors (ECT0

Honda Engine Coolant Temperature Sensors ECT Types
Depending on the year of the Honda, there can be multiple sensors that send information to the onboard computer (ECM/PCM).

Older Honda’s often had 3-4 ECT sensors while newer cars have 2-3 sensors.

Types of ECT Sensor Controls

  • Controls the fan and turns it on at roughly 200 Fahrenheit degrees.
  • Controls the fan when the engine shuts off; turns on at roughly 225 Fahrenheit degrees.
  • Temperature sending unit that sends data to the gauge.

The sensor on the thermostat housing will turn on the fan when the engine is off if the temperature is roughly 225 degrees Fahrenheit.
Causes and Fixes P0118 Code Honda ECT Location
Each sensor will report data on a temperature for a different task.

Newer vehicles have the sensor relocated on the engine and on the radiator, with one sensor doing multiple tasks.

Having a sensor report data for multiple inputs such as the gauge and fan help to reduce the number of sensors needed.

The sensors still do the same task as they did on older cars but with one sensor doing multiple jobs.

P0118 Code Honda Symptoms

  • Low Power
  • Rough Idle
  • Hard To Start
  • Temperature Gauge Doesn’t work
  • Fan On Constantly
  • Fan Doesn’t work

How to Fix a P0118 Code Honda

The first step to fixing a P0118 in a Honda is to locate all the temperature sensors for the year and model of the car.

Doing a Google search should bring up the sensor’s location and the data they report to the onboard computer ECM.

Voltage can be checked at each sensor to be sure it is at 5-volts and if there is a break in the wiring.

Most often, a sensor has gone bad and needs to be replaced.

Narrowing down which sensor is bad will make the job easier, but often many mechanics will swap out sensors until the code clears.

A temperature sensor can also be tested to see if it is good or has failed.

Have you had a problem with a Honda P0118 OBDII Code? Let us know your thoughts below.

Category: General Automotive Repair Honda

About Bob Thomas

Bob Thomas is an automotive mechanic with 30 plus years experience. He is a contributor to several publications and has written many articles on automotive maintenance and repairs. He also has created many auto repair videos on YouTube.

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