What Sensors Can Cause A Car Not To Start?

Anyone who owns a car knows, at the very least, that a car needs a healthy battery, fuel in the tank, and something called a starter motor and spark plugs to start. But what if you’ve used all the ticks on your checklist, and everything seems fine, but your car’s engine doesn’t want to start?

 Modern cars come with an ECU, an engine control unit, which is an on-board computer that manages your car’s vital data and is fed by a bunch of sensors that gather information about your car’s performance, particularly the engine, to ensure that it operates optimally and to provide valuable diagnostic data when things go wrong.

Overview Of What Sensors Can Cause A Car Not To Start

Sensors on your car are not only data-collecting tools but also intended as guardians, protecting your engine’s working parts from damage.

 For example, the oil pressure sensor can prevent your car from starting due to insufficient oil needed to lubricate your engine.

 Your mass airflow sensor (MAF) may be the culprit. If it is dirty or faulty, it will not detect that your air-to-fuel ratio is correct and will prevent the engine from starting. The crankshaft position sensor controls fuel injection or ignition timing for proper starting and engine operation.

 The camshaft position sensor enables the engine controller to determine the ignition point and calculate the crankshaft drive position, which is critical for correct starting.

 Engine temperature is critical to normal operation. The coolant temperature sensor checks the coolant temperature and feeds data back to ECU to control fuel delivery and timing.

Read more: Does Cruise Control Save Gas?

What Sensors Can Cause A Car Not To Start? 


Common Sensors That Can Cause a Car Not To Start

A handful of engine sensors, mainly responsible for controlling fuel, air, and ignition, are essential for your engine to start. These are the most common and vital sensors that affect engine start. If any of these sensors fail, you will see the engine light illuminate on your dashboard.

Oxygen Sensor

Sometimes also called the O2 sensor, this important sensor checks for unburnt oxygen in your exhaust system. This lets the ECU know whether the fuel mixture is burning too rich or too lean and assists in adjusting fuel and air to the correct levels.

 Depending on the engine in your vehicle, such as a V-6 or V-8, you may find up to four of these sensors. Should any of the sensors in the cylinder block or after the catalytic converter fail due to damage or dirt, your engine can experience a catastrophic failure.

 Although this sensor failing will not typically prevent an engine from starting, it is a critically important instrument for ensuring the engine’s smooth running. It can therefore lead to other problems which may cause starting problems.


Mass Air Flow Sensor

This sensor notifies the car’s computer about air levels in the engine. An increase in airflow will adjust fuel flow to keep the ratios optimal.

 Unfortunately, the MAF sensor is prone to carbon buildup with time due to engine combustion and dirt picked up from road surfaces.

 Suppose the dirt or carbon buildup causes the sensor to get too contaminated to measure the airflow effectively.

 In that case, it will send a bad signal to the computer and prevent the car’s engine from burning fuel efficiently. It can also stop your vehicle from starting properly.

Crankshaft Position Sensor

Before the electronic sensors became available, part of this sensor’s function was managed by a distributor, which had to be adjusted manually to line up the timing mark on gasoline-driven engines. Mounted on a crank pulley, camshaft, or flywheel, it monitors engine timing.

 The crankshaft sensor works together with the camshaft position sensor in a four-stroke engine to synchronize the relationship between the valves and pistons and ensure the fuel is injected at the correct time.

 It’s also used to measure engine speed displayed on the instrument panel’s rev counter on your car’s dashboard. If this sensor fails, it will cause the engine to fail when starting.

Camshaft Position Sensor

The camshaft position sensor (CPS) checks for the precise position of the crankshaft drive by measuring when the first cylinder hits the top dead point.

 This is necessary for fuel injection timing and control cylinder-selective knocking, which is caused when the air-fuel mixture combusts prematurely.

 A faulty CPS will cause the engine light to come on, and the control unit will go into emergency mode, possibly preventing the engine from starting.

Coolant Temperature Sensor

If this sensor fails, it can send either a permanently cold or hot signal to the ECU, which may cause the computer to balance the fuel mixture calculations and the timing falsely.


While this sensor failing will not prevent an engine from starting, it could make starting difficult. The car could use more gas than needed and cause black smoke to exit the exhaust.

Sensors Can Cause A Car Not To Start


Other Factors That Can Cause A Car Not To Start

Although a car’s electronic sensors primarily monitor and adjust engine ignition and performance, they are by no means the only causes that prevent a car from starting.


In fact, there are some more common reasons why a car won’t fire up.

Battery Problems

Bad batteries are the biggest culprit preventing a car from starting!


Symptoms of your battery being either partially discharged or faulty include sluggish starting, flickering or dim lights, strange acidic smell, or the engine won’t turn when turning the key. It might also start successfully for a few seconds and then die.


The battery light on the instrument panel will usually indicate a bad battery. Check that your battery is charging using a voltmeter, test and tighten battery terminals or get a professional to test and replace the battery if necessary.


The battery is often not the culprit, even if it is dead. The alternator, the device that generates electricity and is responsible for keeping your battery fully charged, might not be working, causing your battery to drain and preventing you from starting the engine.

Fuel Problems

If your engine cranks when turning the key but won’t kick into life, it could be that it’s starved of fuel. This can be as a result of a faulty fuel pump, a blocked fuel filter, and sometimes even contaminated gasoline. Sometimes it can be caused by defective or clogged fuel injectors.


Starter Motor Issues

The starter motor usually goes bad and fails progressively with time. Early symptoms can include a whirring, grinding, or clicking sound when turning the key. This might happen intermittently or suddenly and is an early indicator of a faulty starter motor. This will usually need you to call a professional.



Sensors are vital for the proper functioning of a car’s engine. Every vehicle has unique characteristics with ECU computers that behave differently to provide optimal performance and protect your engine from damage.

 The most common sensors in modern motor vehicles include oxygen and mass air flow sensors, crankshaft and camshaft position sensors, and the critically important coolant temperature sensor that constantly monitors engine temperature to avoid engine damage from overheating.

 Fixing or maintaining car sensors is not typically recommended for the average layman. Besides, many of these sensors are housed inside the engine compartment and require special tools to remove and replace.

 Instead, watch the engine light, indicating something is up with the engine or sensor. Take your car to a garage or auto electrician if you suspect a problem with one of the sensors. It could end up saving you bags of money!

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