Can a bad coolant temperature sensor cause car not to start?

bad coolant temperature sensor

Car owners are often faced with the dilemma of starting their vehicle. One possible reason for this is a faulty coolant temperature sensor, which can cause your car not to start. If you suspect that your coolant temperature sensor might be at fault, here’s what you need to know about it.

What is a coolant temperature sensor?

A coolant temperature sensor is an electronic device that detects the temperature of your car’s engine coolant. It’s especially important for knowing when to give power to the fuel injectors so your engine can start during cold months. When it comes in contact with air, it will have a high resistance and won’t conduct electricity very well—this lets you know that there isn’t enough heat from your car’s motor. In this way, it acts as a safety mechanism by making sure that your engine doesn’t get too hot or catch fire. This information will be displayed on the coolant temperature gauge on your dashboard.

How does a bad coolant temperature sensor affect my vehicle?

When you turn on your ignition, the ECU sends a signal to the coolant temperature sensor asking for its current reading. Every time it gets this request, it sends an electronic response back to let them know whether or not it is working.

However, if it doesn’t receive enough power (varying between 4.5 and 5 volts), then the sensor will return an error code indicating that there’s a problem with it. This means that you won’t be able to start your vehicle because of the faulty coolant temperature sensor. The type of code that you’ll get after this happens depends on what kind of system your car uses:

  • An analog AC system will display “low input” on your dashboard.
  • A digital DC system will display “coolant temp. sensor” on your dashboard.
  • An engine control unit (ECU) will display “Check Coolant Temp Sensor” or “Coolant Temp. Sensor”. It will also show the OBD error code P0135 if you have a generic car, or P0420 if you have an American vehicle that uses OBD II protocols.

What causes my coolant temperature sensor to fail?

If your car’s coolant temperature sensor is faulty and doesn’t work, it can be for one of several reasons:

  • Your ECU might not be able to send enough power to the analog AC system of the coolant temperature gauge. This happens if your car’s voltage regulator malfunctions or there’s a short circuit in your electrical system.
  • The coolant temperature sensor has a low resistance, which means that it’s not sending any signal back to the ECU or other devices. This happens when there’s a break in the wiring system.
  • Your car might have a problem with its coolant temperature gauge itself—it might be broken, for example. If you suspect this is the case, get it checked by an expert mechanic before going on with your regular schedule of activities.

What are some signs that my car’s coolant temperature sensor isn’t working?

You can tell whether or not your car has a faulty coolant temperature sensor just by checking if it has these problems:

  • The engine takes longer than usual to start.
  • The engine misfires and shakes violently when you try to start it, or if it’s running.
  • The engine cranks but doesn’t start on its own (i.e., the starter motor has a hard time turning).
  • You can hear clicking sounds from under your bonnet as you turn on the ignition of your car.
  • Your dashboard warning lights come on after you try to start your vehicle.
  • You see error codes that deal with the coolant temperature sensor such as “coolant temp. sensor” or “low input”.

What should I do if my car’s coolant temperature sensor is faulty?

If you suspect that your coolant temperature gauge isn’t functioning properly, get it checked out by an expert mechanic right away. This is especially important if you want to prevent problems from arising in the future, including the possibility of your engine overheating or catching fire.

An independent mechanic can tell you whether there’s a problem with your car’s coolant temperature sensor and make the necessary repairs. You might consider getting a warranty for your vehicle to reduce the cost of future repairs by up to 100%!

How much does it cost to replace a faulty coolant temperature sensor?

The price of replacing a faulty coolant temperature gauge depends on where you live and which kind of system is installed in your car:

  • If you have an analog AC system, then it will typically cost between $90 and $180.
  • If you have a digital DC system, then it will typically cost between $110 and $210.
  • If you have an ECU in your vehicle, then this will typically cost between $110 and $210.
  • If you have an engine control unit, then it will typically cost between $130 and $250.

What are the extra costs?

The price of replacing a faulty coolant temperature sensor is just for labor and doesn’t include any other additional costs such as:

  • Parts such as wire harnesses, connectors, switches, etc.
  • Repair tools such as wrenches or socket sets. You might need to get these if your car has bolts in its engine bay that require special sockets to open them up.

How to replace the coolant temperature sensor in your car?

Getting a faulty coolant temperature gauge replaced is a job best left to professionals. In the past, it has been recommended that people with limited experience trying to handle this sort of work should seek help from somebody who knows what they’re doing.

You can do this on your own if you have certain skills and tools. To replace a faulty coolant temperature sensor:

  • Relieve the pressure in your cooling system by draining all of the fluid into a container. You can use an oil catch pan for this purpose. Do not forget to put some baking soda on top of the radiator before draining so as to neutralize any leftover acids or chemicals.
  • Disconnect the negative battery cable from your car’s terminal post so as to prevent the electrical system from turning on accidentally.
  • Locate and remove the faulty coolant temperature gauge in your engine bay. You might need to use a wrench or socket set to do so.
  • Unplug your new coolant temperature sensor by disconnecting its electrical connector, if possible. If you cannot undo the connector, then just unplug it as best as you can so as not to create any extra work for yourself later on.
  • Pin point and connect your new coolant temperature sensor (if there is no connector, plug it in and secure it tightly and safely). Make sure that all connections are fully seated before moving on to the next step of connecting the negative battery terminal again.
  • Make sure that your vehicle’s cooling system is filled with coolant and that you have a working coolant temperature gauge in your engine bay.
  • Start your car and check that the new fault has been fixed. If it continues to appear even after doing this, then there might be something else going on inside of your car’s electronic systems. Consider getting professional help from an independent mechanic as soon as possible if this is the case.

Why you should get an oil change every 3,000 miles or six months, whichever comes first?

An oil change does not need to be performed every 3,000 miles or six months. This date is only recommended by manufacturers and has nothing to do with how frequently your vehicle needs an oil change.

If you’ve noticed that something is wrong with your car’s radiator then it’s time to consider getting a new coolant temperature sensor for your engine bay. If you have any queries or doubts about the process, then feel free to ask an independent mechanic for help.


A faulty coolant temperature sensor can cause a car to stop starting. This will happen if the gauge fails to respond when you’re trying to start up your vehicle or it reports an incorrect reading.

If you need help with this repair, then visit your local mechanic and make sure that they know what they are doing before allowing them access to your car. Don’t take any shortcuts here as this part is vital for keeping you safe on the road.

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