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What Sensors Can Cause a Car To Not Start?

What Sensors Can Cause a Car To Not Start?

Cars are complicated machines with lots of sensors that ensure things run smoothly, but if something goes wrong, a sensor could prevent your from starting.

Are there sensors that can cause a car not to start?

There are many sensors that might stop your vehicle from starting. A few of these include the crankshaft position, brake pedal position, camshaft position, mass air flow, manifold absolute pressure, oil pressure, fuel rail pressure, and throttle position sensors.

Cars have become increasingly more complicated over the years, meaning that modern cars have tons of sensors making sure all of their complex systems and parts are working as they should.

However, if your car isn’t able to start, one of these sensors could be to blame. So, which sensors are the most likely to prevent your car from starting and what are they there for in the first place?

What Sensors Can Cause a Car To Not Start?

There are a variety of different sensors in your car that might prevent it from starting, all with different jobs. However, no matter what each one does, if any of these sensors malfunction, it could easily stop you from starting your car.

Crankshaft Position Sensor 

The most likely sensor that might cause your car not to start is the crankshaft position sensor, which keeps track of the rotational speed and position of the crankshaft. 

This is incredibly important, as the crankshaft is what converts the up and down motion of the pistons in the engine into the rotational energy eventually used to rotate a vehicle’s wheels.

By monitoring the position and speed of the crankshaft, the crankshaft sensor gathers the information and sends it to the vehicle’s engine control unit, which in turn, uses the information to control things like fuel injection and ignition system timing. 

The role it plays in the ignition system is why this sensor is one of the most likely to cause you car not to start. If the sensor is not working correctly, the engine control unit won’t have the information that it needs to start the engine properly, preventing the vehicle from turning on.

Camshaft Position Sensor

The camshaft position sensor, which monitors the speed and position of the camshaft, is another sensor that could potentially cause you car not to start 

The camshaft controls the opening and closing of the intake and exhaust valves above each piston, playing in integral role in the operation of the engine.

Camshaft Position Sensor

As the camshaft rotates, the camshaft position sensor monitors its movement and sends it to the vehicle’s engine control unit where it is used together with the data collected from the crankshaft position sensor to control and manage the firing sequence of the cylinders in the engine. 

Again, because this sensor plays such an integral role in the ignition process and the general functioning of the engine, the camshaft position sensor is another sensor that could easily prevent your car from starting.

Brake Pedal Position Sensor

As its name suggests, this sensor monitors the position of the brake pedal with the purpose of making sure that your vehicle’s brake lights turn on when you press down on the brakes.

However, when this sensor notices that you are pressing down on the brake pedal, it not only sends a signal to turn the brake lights on, but it also informs your vehicle’s engine control unit, which can often causes problems for cars with push to start ignitions.

For safety reasons, in order to start most push to start vehicles, you press the ignition button while holding down the brake pedal. This doesn’t seem like much of a problem, but if your brake pedal position sensor is malfunctioning, it will be unable to register that the brake pedal is being pressed, causing the car not to start.

Manifold Absolute Pressure Sensor

The manifold absolute pressure sensor basically measure the amount of pressure in the engines intake manifold. 

Internal combustion engines work by combining air and fuel together in a cylinder,  which in turn combusts and moves the engines pistons. The air that is combined with the fuel in this process comes from the intake manifold.

If the manifold absolute pressure sensor isn’t working properly, the engine won’t know how much air is in the manifold or how much fuel it should send to the cylinders. Without the right proportion of air and fuel, the engine won’t be able to start.

Mass Air Flow Sensor 

The mass air flow sensor is quite similar to the manifold absolute sensor with most modern cars having one, the other, or both, in the case of some turbocharged vehicles.

Instead of measuring the pressure in the intake manifold like the manifold pressure sensor does, the mass air flow sensor measures the amount of air that moves between the air filter to the intake manifold and into the engine. 

Mass Air Flow Sensor 

This is again incredibly important, as if you mass air flow sensors does not work, the engine control unit will not have enough information to make sure that the right amount of fuel is combined with the right amount of air in the cylinders, causing you vehicles engine not to run properly or potentially preventing it from turning on in the first place.

Fuel Rail Pressure Sensor

The fuel rail pressure sensor is a sensor that measures the the fuel pressure in the fuel rail, which is essentially the tube that feeds fuel from the gas tank into your car engine’s fuel injectors.

By measuring the among of fuel flowing through the fuel rail and sending it to the vehicle’s engine control unit, the data can be used to ensure that the right amount of fuel is being sent when needed.

However, if this sensor malfunctions and engine control unit is unable know or control the proportion of fuel and air it needs to put into the engine. If the proportion of fuel to air leans too far to one side, this could easily cause your car to stall, turn off, or not even start in the first place.

Oil Pressure Sensor

Another sensor that could easily malfunction and cause you car not to start is the oil pressure sensor, which measures the oil pressure and ensures that engine is staying sufficiently lubricated.

All engines need to be properly lubricated if you want them to continue to work as intended, so oil needs to constantly be circulated through the engine at all times. If oil is circulating properly, the oil pressure will remain constant and at the correct level. 

However, if your oil pressure suddenly drops or the sensor isnt’t functioning right, your engine may think that there isn’t enough oil to keep everything sufficiently lubricated. This could easily cause you car not to start in an attempt to preserve the engine from damage that could come from being insufficiently lubricated.

Throttle Position Sensor

The throttle position sensor is yet another sensor that could cause your car not to start. This sensor helps manage the amount of fuel that is injected into the engine by monitoring the position of the throttle valve.

This sensor works to make sure that the right amount of air and fuel are enter the engine so that it performs at its best. However, if it malfunctions and the sensor registers that the throttle valve is wide open, it will prevent your car from starting.

How Do You Know Which Sensor Isn’t Working?

If your car isn’t starting and you can’t figure out why, unfortunately, the best thing for most car owners to do is to take their vehicle to an auto repair shop and have them run a diagnostics check. 

Most of the time, it is very difficult to determine which sensor is malfunctioning just based on how you car is affected, as many sensor malfunctions can often look quite similar even if the sensors do drastically different jobs. 

Taking your car to an auto repair shop will allow a mechanic to plug directly into your car and see the specific diagnostic codes that tell you exactly what is going wrong. Once you run the diagnostics test and you know what sensor is causing the problem, fixing the issues is as simple as a quick part replacement.

Key Takeaways to What Sensors Can Cause Your Car Not to Start

Cars are incredibly complicated machines that require a lot of different sensors to make sure that everything is running as it should.

Sensor malfunctions can often prevent your car from starting.

Common sensors that can cause a car not to start are the crankshaft position, brake pedal position, camshaft position, mass air flow, manifold absolute pressure, oil pressure, fuel rail pressure, and throttle position sensors.

In order to find out which sensor is malfunctioning, you should go to an auto repair shop and ask them to run a diagnostics test on your vehicle.

Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!