3 Common causes for a car not to start. How to Troubleshoot

Updated: May 29, 2022
The three most common causes for a car not to start are:
  • Battery that has failed or is low on charge, or its cables/terminals are loose or corroded.
  • Failed starter motor.
  • Problems with the starter motor circuit and devices that allow the starting system to operate, including a starter control wire/terminal, transmission range switch (neutral safety switch), ignition switch, brake light switch and immobilizer.
Car won't start
It is frustrating when your car won't start. You are turning the key and... nothing happens. Almost every car owner has experienced this. There are many things that can go wrong with your car, but no need to worry, there is a solution for almost every problem.
Of course, you can call your local automobile association or a towing service and have your car towed to a local repair shop, but if you want to know why it doesn't start, read further.

How to troubleshoot: The process that goes on from the moment you put the key into the ignition to the point where the engine is running involves a few steps. Once you know at which step things go wrong, you will have a better idea what causes your car not to start and what to do. If your car starts with a "Start" button instead of an ignition key, follow to this article Why a car won't start when you push the Start button?
Answer these questions; if the answer has a link, follow it; if not, continue to the next questions.

What happens when you are trying to start the engine?

Ignition ONIgnition key
1. Can you turn the key in the ignition? Yes No
2. When you turn the ignition ON:
Do the lights come on in the instrument panel?
Yes No
Does the "Security" or Key-shaped warning light stay on or blink repeatedly? Yes No
Does the "Check engine" light come on? Yes No
3. What happens when you turn the ignition key to the "Start" position?
- Nothing happens, the engine won't turn over.
- There is a click (or repeated clicking) but the engine won't turn over.
- The engine turns over (cranks) very slowly.
- The engine cranks progressively slower, then just clicks repeatedly.
4. Does it help if you jiggle the key in the ignition while starting? Yes No.
If the starter cranks normally, but the car won't start, read this guide: The engine cranks but won't start »

What to check if the car doesn't start

Does the car battery have enough charge? Read the next paragraph on how to check the battery.
If the car doesn't start with the transmission in "Park," does it start in "Neutral"? Sometimes a car won't start in "Park" but starts in "Neutral" because of a problem with a transmission range switch. Read more: Why a car won't start in Park but starts in Neutral?
Is the "Security" or key-shaped light in the instrument panel staying on or blinking? Read below about the security light.
Does your car have an anti-theft system that for some reason doesn't allow the car to be started?
Are the car battery terminals tight and not corroded?

How to check the battery

Here is a simple way to check if the battery is low on charge: Turn the windshield wipers on. If they move slowly, much slower than usual, the battery is probably low on charge. Look at the dash lights. If they dim when you are starting the engine or when you are turning the wipers on, the battery is most likely discharged.
Measuring battery voltageMeasuring battery voltage
Watch this video example.

You can also check the battery voltage with a multimeter. A fully-charged battery should have at least 12.6 Volt. If the voltage is less than 12 Volt, the battery is low on charge.

Turn the headlights on and measure the voltage again. If the voltage drops below 12 Volt within 30 seconds, the battery is too weak to start the car.

If the battery is relatively new, it can be recharged. One way to do this is to boost your car's battery from another car or a portable booster, start the car and let the engine run for a while. Read below about boosting the battery.

However, if the battery is more than 5-7 years old, it might be completely dead, so even if you boost it, it won't take charge and the car will not restart again after you shut it off. In this case, you might need a new battery. A problem with the alternator can also cause the battery to be low on charge.

We are often asked can a bad alternator cause the car not to start? Not directly: If the alternator is bad it will not recharge the battery and after a while the battery will be too low on charge to start the car. However if the battery is good and charged, the car will start even with a non-working alternator.

The key won't turn in the ignition

If the key won't turn in the ignition, it could be for a couple of reasons:
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Often this happens when the steering is locked by the ignition lock with the front wheels turned aside (e.g. when parking on a hill) or when one of the front wheels is pushed against something (e.g. curb). In this case, try turning the steering wheel left and right while gently jiggling the ignition key - this might help to release the steering lock.

Another possibility is that there is a problem with the ignition lock or the key itself. This happens; the key and the lock mechanism wear out over time. Try using a spare key. Sometimes lubricating inside the key slot with something like WD-40 helps. If nothing works, your local dealer is the best place to call.

No lights on the instrument panel

If you turn the ignition on and no lights come on on the instrument panel, it means that there is no power coming from the battery. It could be a dead battery, loose battery terminal or something like a bad ignition switch or blown main fuse.

Turn the headlights on, if they work, means the battery has power, so the problem could be with the ignition switch, fuses or wiring between the ignition switch and battery. If the headlights don't work, the battery could be completely dead. Boosting the battery may help; read below.

"Security" or Key-shaped light stays on or flashes repeatedly

Security light flashingSecurity warning light
Today's cars are equipped with an immobilizer or a security system that allows starting engine only if the correct key is used.
The ignition key has a chip inside with the security code. When you insert it into the ignition, a sensor for the security system verifies the code. Normally when you turn the ignition on, you would see a "Security" light coming on for a short time and then it would come off. This means that the code in the ignition key is correct, and the car is allowed to start.

If when you turn the ignition ON, the "Security" light stays on or flashes repeatedly, it means that your car security system does not recognize the key or there is some problem with some part of the security system itself. You can find more information about the immobilizer in your owner's manual.

Some GM cars, for example, had a problem with the security system sensor located at the ignition lock. Sometimes, the key just needs to be reprogrammed. In some older cars, there was a simple procedure to re-learn the key that would fix this problem. You can find the information on how to re-program the key in your owner's manual or just Google it. Try the spare key and if nothing works, your dealer is the place to call. In most modern cars, only an authorized dealer can reprogram the key.

The "check engine" light does not come on

Check Engine LightCheck Engine light
When you turn the ignition ON before starting the car, the "Check engine" light comes on indicating that the engine computer called PCM, ECM or ECU is powered on.

If the "Check Engine" light does not come with the ignition ON, it's possible that there is no power coming to the engine computer (e.g. due to a broken wire, faulty main relay, blown fuse) or there is a problem with the engine computer itself. Read more: how to check a fuse.

The starter won't crank

If nothing happens when you turn the ignition key to the "Start" position, it means that the starter motor doesn't turn over the engine. Most commonly this could be caused by a dead battery; read above How to check the battery.
If the battery checks out OK, but the starter still won't crank, there could be a number of possible reasons. Here are some of them:

The starter motor itself or a starter solenoid could be bad - it's a common problem at higher mileage. Read more about the starter motor.
The ignition switch could be bad - it's a common problem. An ignition switch is an electrical switch installed at the back of the ignition lock mechanism. If jiggling the key in the ignition helps start the car, the ignition switch should be checked first. See this video.
The starter solenoid control wire could have a bad connection.
A problem with a neutral safety switch. If a car doesn't start with the transmission in Park, but starts in Neutral, it could be caused by a problem with a neutral safety switch or the shifter cable. For example, watch this video.
Read more about the starting system.
A problem with the vehicle's security system or some other electronic control module (e.g., ECM, BCM) may also prevent the starter from operating.

I can hear a click, but the starter won't crank

It's a very common problem: you turn the key to the "Start" position, but the engine won't crank; all you hear is a single click or repeated clicking coming from the engine compartment. Very often this could be caused by a weak battery. Read this paragraph above: how to check the battery. A poor connection or corrosion at the battery terminals or cables can also cause this issue. Even a bad connection between the negative battery cable and the engine (bad ground) can cause the same symptoms.

Check the battery terminals to make sure they are tight and not corroded. Here is a photo of a corroded battery terminals. If the battery is OK and the battery terminals appear clean and tight, the starter solenoid or the starter motor itself could be the problem. A starter motor is common to fail at higher mileage. Read more: Starter motor, starting system.

The engine cranks very slow and won't start

This also might be caused by a weak or discharged battery; read the paragraph above on how to check the battery. If the battery is OK, the battery cables could have a bad connection at the terminals or the starter motor itself could have a problem.

Sometimes, the starter motor armature bushings wear out and the starter armature rubs against the field coils inside the starter motor; this will also cause the starter motor to crank very slow. If this is the case, the starter motor will need to be rebuilt or replaced.

Another possible reason is that the engine could have an internal mechanical problem (e.g., lack of oil, very old engine oil). Check engine oil, just in case. Read here on how to check engine oil.

The engine cranks progressively slower, then just clicks

If the engine cranks slower and slower until it just clicks, it means the starter motor doesn't have enough power to turn over the engine. This problem should be fairly easy to diagnose, as there are just two cables (positive and negative) to deliver the electric current from the battery to the starter motor.

Once again, a weak battery is the most common culprit in this case. A bad starter motor can also cause this issue. Poor connection or corrosion at the battery terminals or bad battery cables can cause these symptoms too. If the battery is old, you might want to start with replacing the battery; a new battery is not very expensive.

Jiggling the key helps start the car

Sometimes, if there is a problem with the ignition lock or ignition switch, jiggling the key may help. For example, there was a common problem in older Ford Escape trucks where a bad ignition lock module caused the vehicle not to start, but jiggling the key would help. Watch this video.

Boosting the car battery

Boosting a car Boosting a weak battery from a good battery in another car.
Boosting a car is a way of starting a car with a weak battery using power from a good battery in another vehicle or a booster pack. You will need jumper cables and another car with a good battery or a portable booster or booster pack; it's a fairly quick procedure.

Check your owner's manual for the correct way to connect the cables, because different cars have different locations of the positive and negative connection points. It's important to connect the jumper cables the right way, so follow the instructions carefully. Be careful, we know many cases when accidentally mixing the positive and negative cables while boosting a car caused more damage. For example, several fuses might be blow as a result.