Why a BMW Won’t Start

A BMW will not start for several reasons, such as a dead or low battery, a faulty starter motor, a malfunctioning ignition switch, fuel system issues, engine mechanical problems, and an electronic control module (ECM) failure. It’s important to inspect the vehicle by a certified BMW technician to diagnose and repair the issue and ensure its correct function.

BMW no-start problems range from no power to the yellow exclamation mark on the dashboard, clicking noise when you press start, or you may even hear several clicks. Sometimes, your BMW will not start when cold; the lights and radio may work, but the engine doesn’t. Sometimes, your BMW may not even start with a jump start.

Symptoms

• Pushing START will not start the engine.
• BMW won’t start. All lights are dead / off.
• You insert the key, and nothing happens.
• BMW engine won’t turn over, makes a clicking noise
• The car won’t start after changing the battery.
• BMW won’t start an exclamation mark
• BMW won’t start in cold weather
• EML Light On, BMW refuses to start
• BMW lights flashing, no start
• BMW won’t start showing the key symbol on the dashboard

Common Causes

There can be several reasons why a BMW will not start; some of the common reasons include the following:

1. Dead battery: A dead battery is one of the most common reasons for a car not starting. The car’s battery provides power to the starter motor, which starts the engine. If the battery is dead or has a low charge, the starter motor will not have enough power to start the engine. Test the battery first.
2. Bad starter motor: The starter motor is responsible for turning the engine over when you turn the key. If the starter motor is faulty, the engine will not crank, and the car will not start.
3. Faulty ignition switch: When turning the key, the switch sends power to the starter motor. If the ignition switch is faulty, it will not send power to the starter motor, and the car will not start.
4. Fuel system issues: If the fuel system is not delivering fuel to the engine, the car will not start. Various issues, such as a clogged fuel filter, a faulty fuel pump, or a malfunctioning fuel injector, can cause this.
5. Engine mechanical issues: If the engine has a mechanical problem, such as a seized piston or a thrown rod, the engine will not start.
6. Electronic control module (ECM) failure: The ECM, also known as the DME, controls many of the car’s electronic systems. If it is not functioning correctly, it can prevent the car from starting.

It’s important for a certified BMW technician to inspect the vehicle to diagnose and repair the issue and ensure its correct function. A BMW may not start for many other issues, such as:

• Weak fuel pump
• Engine temperature sensor / PCM Coolant Sensor
• Worn spark plugs
• Bad ignition coil
• Defective starter
• Electrical issues
• Damaged key
• Weak key fob battery
• Bad Fuel Pump or Relay

Troubleshooting

Check Battery

Next, you need to check the battery. The problem is usually the battery if your lights or dashboard do not power up. SIGNS OF BAD BMW BATTERY include No noise, no lights, no radio, no dashboard, and no click.  A partially Discharged Battery will turn lights on, and a car will crank or click without enough power to start the engine.

The problem may still be the battery, even if your lights come on and the radio works. The battery should still be checked. The battery may have enough power for low-consumer electronics such as lights and radio, but the engine should not be turned over.

There is usually a problem with BMWs with batteries over seven years old or with a parasitic draw. THE POSSIBLE SOLUTION is to jump-start or Trick-Charge the battery. Use the jump-starting terminals under the hood. Do not connect the jumper cables directly to the battery.

Charge Battery

Another option is to use a trickle charger to charge the BMW battery.

This procedure requires anywhere from five to twenty-four hours but is preferred to bring a discharged BMW battery back to life. Once the battery is fully charged, the car should start without any issues unless your BMW battery has a damaged cell. If the same symptoms come back in a few days, there is a chance that the battery is not holding a charge.

If the battery is new, the problem can be due to a parasitic drain. Your battery may be at the end of its life and needs to be replaced. If your battery is over seven years old, consider changing it to get stranded away from home. Follow this guide to replace a BMW battery yourself and perform battery registration.

Check Fuses / Relays

Your BMW may not start due to a blown fuse or a bad relay. Checking the fuses on a BMW is very easy. You can remove the fuse and visually inspect the fuses. You can also check with a digital multimeter. BMW fuse boxes can be found in one or more of the following locations:

• Engine Bay
• Side or under the dashboard
• Trunk area

Below is a list of fuses that you need to remove and check. Always check BMW fuses with the key removed from the ignition.

FUSES TO CHECK

• Starter Fuse / Relay
• Immobilizer / Security Fuse
• Fuel Pump Fuse / Relay
• DME / DDE / Engine Electronics Fuse
• The ignition switch control module
• Alarm system
• Main Relay
• Engine control module (ECM)
• The ignition switch control module
• Central locking system
• Engine management

You also want to check the relays, especially for the starter and fuel pump. Relays cannot be visibly inspected. You can either swap identical relays or replace them.

Inspect Battery Safety Terminal BST

The Battery Safety Terminal can also prevent a BMW from starting. It can detonate if you were in an accident, rear-ended, hit a curb, or even during battery replacement.

Symptoms of a bad BST cable include BMW lights, accessories, and radio work, but the car won’t start. The BST is at the end of the positive cable connecting to the positive battery post. It has GAS and IGNITER that explodes if it detects an impact.

If you are in an accident, the BST will disconnect the starter and the alternator. You will also get a fault code in the airbag control module and the airbag light. Locate the battery in the trunk to verify if the BST cable is bad. Pull the red cable from the BST / battery-positive clamp. If the cable is easily removed, the BST explodes and needs to be replaced. 

You can manually push the cable back into the BST or find a way to reconnect it securely, which will allow you to start the car. Note that the airbag light may stay on after this problem and require a BMW scanner to reset it. Purchasing a new BMW BST repair cable and replacing it yourself is possible.

BMW dealers will sell you a new cable, usually at a much higher price than you find online. This repair costs anywhere from $500 to $900 at a repair shop. You can save hundreds of dollars by doing this repair yourself.

Check Fuel Pressure

If your BMW cranks but does not start, you must check the fuel pressure. The test is straightforward and takes about 15 minutes. Remove the engine cover, and you will find a Schrader valve at the end of the fuel line.

Most BMWs will have a Schrader valve, but a few models don’t. Connect your fuel pressure gauge to the port and look at the indicator when you turn on the ignition or try to start the car.

• Typical BMW Fuel Pressure: 50-65 PSI (+/-3)

Spark Plugs / Ignition Coils

If your BMW will not start and then dies, check the spark plugs and coils. Common symptoms of spark plug issues include a BMW won’t start, loss of power, poor fuel economy, and engine misfires.

If you replaced the spark plugs and your BMW no longer works, ensure all the wire harnesses are correctly connected. Do not swap the wires between ignition coils. Each ignition coil wire must connect to the same ignition coil from where it was removed.

Bad Starter

Also, inspect the starter. A starter will prevent an engine from turning over. Tapping the starter with a hammer may allow you to start the engine several times.

Key / Immobiliser / Anti-theft

Your car won’t start because of the BMW alarm system or the key. Try locking and unlocking the car several times, then try starting it. A defective key can sometimes unlock the car but not start the engine. This problem often happens if the key gets wet or is stored in a humid environment.

Don’t drop your BMW key in the water or let it get wet from the rain. It can stop working. You may think the key is fine, but it is not. Grab your spare BMW key and test it to see if it will start the car.

Read BMW Fault Codes

If your BMW does turn on, all your lights, dash, and radio come on, but the car will not start; you can read fault codes.

A fault code may be stored in one of the other modules. A generic (Level 1) OBD-II scanner will not retrieve BMW-specific trouble codes or access other modules. You will need a BMW scanner like the YOUCANIC Full System Scanner to read and clear BMW codes from various modules.

With your BMW scanner, perform a full system scan or health report. A good scanner will allow you to auto-scan all the modules. Once the scan is complete, you will get a report of BMW fault codes. Pay attention to any code that has the status PRESENT or CURRENT.  These will need to be addressed. Codes that show PAST or HISTORY (depending on the scanner) can be erased without any issue.

Troubleshooting by Symptoms

BMW won’t restart after running out of fuel

Yes, any car that runs out of gas will stop running, but the problem here is that after you add gas, the BMW still won’t start. This is because your fuel lines have air pockets.

BMW will not start in cold weather

Sometimes, the BMW may not start when parked outside in cold weather. Typical symptoms include the engine turning over slowly and then starting. You can usually start the BMW by cranking the engine several times or waiting until it gets warmer, but it is not the ideal solution.

The first thing you need to check is the battery. This problem can be due to a battery near the end of its life. Battery performance decreases as the temperature decreases; therefore, it may be harder to start the car if it is cold outside.

BMW won’t start after an accident

A BMW may not restart after an accident due to a Positive Cable Battery Safety Terminal BST. The BST causes a disconnect in the battery-positive cable whenever the car gets in an accident or an impact is detected. This is also known as BST, which stands for Battery Safe Terminal. The battery gets disconnected during a crash to minimize the risk of fire, sparks, and electrical shorts that could happen during an accident.

It generally fires when airbags deploy. It may also fire on its own without any airbags having to deploy. You can bypass the BST by reconnecting the cable. It is recommended to replace the cable as soon as possible.

The airbag module also stores a fault code, so the airbag light stays on. Once you repair or install a new BMW BST cable on eBay, use a BMW-specific scanner to reset the airbag light.

BMW won’t start with a jump box

A BMW may not start even when you connect the jumper box.

This is usually due to two reasons.

1. The battery is completely discharged or short, allowing the starter to get enough juice to turn over the engine.
2. There is poor contact or low-quality jumper cables.

To start your BMW, try connecting the second source of power. A lithium jump box can provide more power to the starter. Another option is to let the helper car jumper cables be connected for at least fifteen minutes. If your battery is short, this can be dangerous. It can cause your old battery to overheat and, in some cases, even explode.

BMW cranks but won’t start

If your BMW cranks, but it won’t start, the problem is often one following.

1. The engine is not getting fuel.
2. No spark at the spark plugs
3. Low compression
4. A bad crankshaft position sensor
5. DME issue

You can start by performing a fuel pressure test—a port on the fuel rail on top of the engine to connect a fuel pressure gauge.

The fuel pressure should be around 60 PSI. Next, you can check for sparks using a spark tester. This requires removing the engine cover and at least one of the spark plugs. Lastly, you will need to check for compression.

BMW won’t start just clicks

A weak battery or a detonated Battery Safety Terminal often causes this problem. Try jump-starting the car or replacing the battery.

BMW won’t start asking for code

If you replace the battery, leave your BMW disconnected for a long time, or replace the instrument cluster, the car may not start asking for a code.

The car will ask for a code when you turn the ignition on. To deactivate this feature, try the following:

1. Disconnect the battery for 10 minutes.
2. Next, connect the battery.
3. Turn the ignition with one click. Do not turn on the dash lights.
4. Wait 10 minutes. A timer will also show on your cluster.
5. Start the car after waiting for 10 minutes.

BMW won’t start when hot

A BMW may refuse to start in warm weather, especially in areas that get very hot on summer days. If you wait for the temperature to drop, the BMW will start without a problem. Accessories and other electronics will work as usual.

Any of the following can cause this problem.

• Immobilizer Problem
• A bad crankshaft position sensor
• Stuck Relay
• Defective Key
• Bad Starter
• Starter solenoid
• Coolant temperature sensor
• Battery connections/ground

To avoid this problem, do not park your BMW directly under the sun on hot summer days. If you have this problem, try jumping-starting your BMW. Test the starter. If the starter is in good condition, check the starter and immobilizer relay.

Next, check connections at the battery and ground points. Poor connections can increase high-temperature resistance, preventing the starter from obtaining enough amperage.

BMW won’t start when the steering wheel is locked

Older BMWs have a mechanical steering wheel mechanism to lock the steering wheel if the key is removed. To get the key to turn or the car to start, move the steering wheel slightly and then turn the key. Newer BMWs with Comfort Access with Start/Stop buttons may refuse to start, and the steering wheel stays locked. You will get a steering lock warning on the instrument cluster, and can’t start the car.

Newer BMW cars have an electronic steering wheel lock that may malfunction. The problem is often caused due to the low voltage of the Electonic Steering Lock (ELV) module.

If you scan BMW fault codes, you will get a fault code in the CAS (Car Access System). If so, your BMW steering wheel will not unlock when the key is inserted into the ignition. Call your BMW dealer to check for a TSB or software update to fix this problem.

If the software update does not fix your problem, there is a good chance that you will need the steering column replaced. As a temporary fix, try locking and unlocking your BMW, then try to start the car. This will often unlock the steering wheel and allow you to start the car.

If you have Comfort Access, insert the key into the key slot or place it near the steering column. If that fails to ensure the battery is fully charged, it is not charged using a trickle charger. Follow these instructions on how to charge a BMW battery.

BMW won’t start or is making a clicking noise

This problem is usually caused by a partially discharged battery. Charging the battery will most likely allow you to start the car. Other possibilities include a bad starter, no fuel pressure or spark, and, in rare cases, a damaged engine.

BMW won’t start after it warms up 

BMW may start fine when it is cold but will refuse to start if it warms up. The car starts fine in the morning. You drive it for 30 minutes or an hour. Turn off the engine.

I tried to start the engine again, but it won’t start now. Any of the following can cause this problem.

• Bad Starter
• Crankshaft Position Sensor
• Camshaft Position Sensor
• Fuel Pressure Issue
• Starter Solenoid

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