Can a Bad Sensor Prevent a Car From Starting?

Today's engines are complex and rely on multiple moving parts that must work together to operate efficiently. However, sensors are an often overlooked component that monitors fuel, electrical, cooling, and emissions systems. Although their job often begins once the engine has already started, there are some sensors that might cause an engine not start.

Noted below are a few of the sensors that, if they fail, could be the culprit of a hard to start issue.

Which Sensors Prevent the Engine from Starting?

Sensors do much more than simply record and send data to the ECU. In fact, most sensors are responsible for actually making the changes to critical systems such as ignition and fuel systems. Since any engine requires the correct air to fuel ratio and ignition timing to start, having a faulty sensor that can't adjust these symptoms on the fly can cause the engine to not start.

There are many reasons why damaged sensors would impact the engine starting process such as:

  • Faulty sensors can keep your engine from starting, but this is often engineered in as a safety measure. For instance, the crank angle sensor or crankshaft position sensor may be located near the transmission belt housing and come in contact with water, which would prevent it from working. This sensor measures the position and speed of the crankshaft to ensure the pistons are timed for the right amount of combustion at the right time. Combustion timing needs to be accurate, or engine damage can occur. If the information isn’t sent to the engine computer, nothing will happen when you try to start the car as a way to prevent damage.

  • Dirty sensors will impact whether your vehicle starts. An example of this is the Mass Air Flow sensor or MAF. The job for this sensor is to let the computer know how much air is in the engine. As more comes in, more fuel is also needed to maintain optimal ratios. Without the correct ratio, the engine won’t run. The MAF can become clogged with excessive carbon build-up from the combustion cycle, or sometimes by road grime. If it is too dirty, it will be unable to correctly measure the air fuel ratio, and cause your car to not start or exhibit other unusual symptoms.

  • Preventing engine damage is another reason that a sensor fault can cause a hard to start problem. The oil pressure sensor on some models may prevent your car from starting if it isn’t working correctly. This sensor lets the computer know the correct oil pressure is present. Since the efficient flow of engine oil is required to maintain proper lubrication, a failed sensor or one that is not able to relay data can trigger a fail safe mode in the ECU. If it sends a signal that the pressure is low, the computer may prevent the engine from starting. If the signal was sent in error or no signal sent at all, it may indicate you have a bad sensor.

Sensors play a vital role in the overall operation of your engine. If you have a situation where the engine is hard to start or will not start at all, have a professional technician from YourMechanic test your sensors if you think one is causing the problem. Chances are it can be replaced so you can get back on the road.


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Corey

16 years of experience
136 reviews
Corey
16 years of experience
Jeep Patriot - Car is not starting - Charlotte, North Carolina
Corey was awesome! Very knowledgeable, he knew what was wrong with my car by just looking at it! He went the extra mile!
Nissan Sentra - Car is not starting - Charlotte, North Carolina
Corey was quick and thorough with his inspection. I usually do not like dealing with mechanics as a female as some try ang get over on you, but Corey was honest and I trust his advice.

Pierre

9 years of experience
187 reviews
Pierre
9 years of experience
Jeep Liberty - Car is not starting - Boston, Massachusetts
Pierre was professional, friendly, efficient and extremely effective. He determined the issue and fixed the problem right away. Highly recommend his service and will absolutely use this company again.
Ram ProMaster 3500 - Car is not starting - Quincy, Massachusetts
Pierre was communicative, transparent, and committed to finding answers to my problem. Even though he was not able to fix the problem, I had more information to bring to a mechanic than ever before and am more informed about where the problem is coming from. Highly recommend!

Pardeep

21 years of experience
863 reviews
Pardeep
21 years of experience
BMW 325i - Car is not starting - San Jose, California
Pardeep is very knowledgable and capable to fix my problem ( car not start due to broken starter). He quickly diagnosed my car and found the issue. Then he ordered the part and replace it soon. The whole process was very smooth.
Ford Explorer - Car is not starting - Fremont, California
Pardeep was very knowledge on my issue. He did a few underhood tests, Then he was able to explain my issue. Unfortunately he was unable to do the repair. I thank him for assisting me with true information that will have me on the road tomorrow.!

Marco

29 years of experience
129 reviews
Marco
29 years of experience
Fiat 500L - Car is not starting - Moreno Valley, California
Marco is amazing! He was able to diagnose the issue with my car and give me a list of work that still needed to be done and list it by priority. Would highly recommend to everyone!
Chevrolet Corvair - Car is not starting - Ontario, California
Marco ... is a top notch mechanic that was able to trouble shoot my problem and get me back on the road. He is a asset to have representing your company.

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