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Code P0118 (Symptoms, Causes and How)


The last thing you want to deal with while driving down the road is a check engine light. But for millions of drivers, that’s exactly what happens every year. So you rush to read the OBD-II code, but so what?

Well, if you have a P0118 code, we explain everything you need to know. From what it means to how to fix it, we’ve got you covered. And if you’re wondering how bad the check engine light is, we’ll tell you all about that too.

What does the code P0118 mean?

P0118 OBD-II Trouble Code Description

Engine coolant temperature circuit: high input

Inside your vehicle is a sensor that reads the current engine temperature and sends that information to the ECM so it can make appropriate adjustments to the fan and other cooling mechanisms. A high intake means the engine is cold and when the engine warms up you get a lower intake.

When your engine detects that the inputs are not reading typical results or are outside of an acceptable range, it may generate a P0118 code. Typically, at this point, the ECM defaults to a position where the engine is providing maximum cooling so that the engine does not overheat.

See also: P0117, P0125, and P0128

Code P0118 Symptoms

check engine light

If you have a P0018 code, the truth is that you probably won’t notice many symptoms. Most of the time, the only thing you’re likely to notice is a check engine light. However, while this is often the case, it is not the only possible outcome. Below we highlight some other possible outcomes.

When your vehicle constantly runs the engine fan and other cooling devices, the result is an overworked engine. This means that fuel economy will decrease, although you probably won’t notice a significant drop.

Causes of Code P0118

Faulty coolant temperature sensor symptom

The most likely cause of a P0118 engine code is a faulty engine coolant temperature sensor.

Although these sensors can last a long time, all sensors eventually wear out. However, if you used regular tap water to mix with your antifreeze instead of distilled water, or if your coolant is extremely old, this could also be a problem.

If the problem is a rusty cooling system, that’s the worst-case scenario. Even if you flush the coolant, the rust will likely return, meaning you will have to replace several components. However, as long as you use distilled water when mixing the coolant, this should not be a problem.

One last potential problem is a wiring problem. Even if the sensor works as it should, if the wires sending the signal to the ECM are corroded, broken, or shorted, it won’t matter. Again, it’s likely a faulty engine coolant temperature sensor, but you can’t automatically rule out a wiring problem.

  • Faulty engine coolant temperature sensor
  • Old/defective cooler
  • Wiring problems

See also: How to wash a radiator

Is code P0118 serious?

As you look at the symptoms, you may wonder if the P0118 code is that serious. If you don’t notice any unusual conditions while driving, how important is it really?

The truth is, even if you don’t notice any unusual symptoms, that doesn’t mean there aren’t problems that can arise if you drive with a P0118 code. First, it applies additional wear to various components.

Your motor fan is not designed to run all the time and excessive use can cause premature wear. And since your engine has no way of telling you that the coolant is getting too hot, you also lost the ability to shut off the engine to protect itself when it overheats.

If you drive with a P0118 code, you probably won’t notice anything wrong, that is, until it gets bad. And since the P0118 code is relatively easy and inexpensive to repair, the last thing you want to do is risk your entire engine on a cheap repair.

How to fix

coolant temperature sensor replacement cost

If you have a P0118 engine code and a faulty engine coolant temperature sensor issue, you can expect to spend between $125 and $175 on repairs if you take it to a professional shop.

However, if you do the work yourself, you can save money as the part usually only costs between $40 and $60.

And when it comes to car work, replacing the engine coolant temperature sensor is usually easier. Refer to the sensor location in your specific vehicle’s factory service manual for more information.

If coolant is an issue, you can expect to spend around $100 to have a mechanic flush the system. Of course, the exact price will depend on the size of the cooling system.

If you plan to do the work yourself, expect to spend $10-20 per gallon of premixed solution. So if your vehicle has a 4-gallon cooling system, you will need to spend between $40 and $80 depending on the coolant your vehicle uses.



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