Why Your BMW Won't Start

Vehicle:   BMW
Difficulty: ⚫⚫⚫⚪⚪
DIY Cost:
Est. Time: 15 min - 3 hours

In this guide, we will look at some of the most common problems that can prevent a BMW from starting and possible ways to troubleshoot or fix these problems yourself.

BMW no-start problems range from no power at all to the yellow exclamation mark displaying on the dashboard, clicking noise when you press start, or you may even hear several clicks.

bmw won't start

 

Sometimes your BMW will not start when it is cold, lights and radio may work, but the engine still doesn't start. In some cases, your BMW may not even start even with a jump start.

Symptoms

bmw service light

BMW no starting symptoms can vary.
 
Here are some of the most common symptoms you may experience if your BMW won't start.
  • 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 shows the key symbol on the dashboard

Common Causes

A BMW may not start for various reasons.

  • 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

Weak Battery

bmw battery dead

Next, you need to check the battery. If your lights or dashboard does not power up, the problem is usually the battery. SIGNS OF BAD BMW BATTERY include No noise, no lights, no radio, no dashboard, no click

Partially Discharged Battery

  • Lights on, a car will crank or click but not 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 not power to turn over the engine.

The is usually a problem with BMW with a battery over 7 years old or has a parasitic draw problem.

POSSIBLE SOLUTION

CAUTION!
- Use the jump-starting terminals under the hood. Do not connect the jumper cables directly to the battery.

Charge BMW Battery

Another option is to use a trickle charger to charge the BMW battery.
 
This procedure requires anywhere from 5 to 24 hours but is preferred to bring a discharged BMW battery back to life.
 
Once the battery is fully charged, it should start the car without any issue 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 7 years old, consider changing it to get stranded away from home.

Follow this guide on how to replace a BMW battery yourself and perform battery registration.

Check Fuses / Relays

bmw not starting due to blown fuse

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 fuses. You can also check with a digital multimeter.

BMW fuse boxes can be found on 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
  • Ignition switch control module
  • Alarm system
  • Main Relay
  • Engine control module (ECM)
  • 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 replays or simply 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, got rear-ended, hit a curb, or even during battery replacement.

Symptoms of a bad BST cable include:

  • BMW lights, accessories, radio work, but the car won't start.

The BST is located at the end of the positive cable that connects to the battery positive 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 airbag light on.

To verify if the BST cable is bad, locate the battery in the trunk. Pull the red cable from the BST / battery positive clamp.

If the cable is easily removed, the BST exploded and needs to be replaced.

You can manually push the cable back into the BST or find a way to reconnect it securely will allow you to start the car.

Note that the airbag light may stay on after this problem and requires a BMW scanner to reset the light.

It is possible to purchase a new BMW BST repair cable online and replace it yourself.

BMW dealer will sell you a new cable as well, usually at a much higher price than what you will 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 it will not start, you need to check the fuel pressure. The test is straightforward and takes about 15 minutes.

Remove the engine cover, and at the end of the fuel line, you will find a Schrader valve.

bmw fuel test port location

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 gauge when you turn on the ignition or try to start the car.

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

Spark Plugs / Ignition Coils

bmw won't start due to bad ignition coil spark plugs

If your BMW will not start or start then dies, check the spark plugs and coils.

Common symptoms of spark plug issues include BMW won't start, loss of power, poor fuel economy, engine misfires.

If you replaced the spark plugs and your BMW no longer works, ensure that all the wire harnesses are connected properly.

Do not swap the wires between ignition coils. Each wire ignition coil wire needs to connect to the same ignition coil from where it was removed.

Bad Starter

Also, inspect the starter. A bad starter will prevent an engine from turning over.

bmw no start

Key / Immobiliser / Anti-theft

bmw won't start

BMW alarm system or the key itself may be the reason why your car won't start.

Try locking and unlocking the car a couple of times, then try starting it.

In some cases, a defective key can unlock the car but still does 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 water or let it get wet from the rain. It can stop working. You may think the key is fine, but in fact, it is not.

Grab your spare BMW key and test to see if it will start the car.

Troubleshooting a BMW that won't start

If your BMW turns on but won't start, one of the first things you need to do is check for fuel pressure, spark and compression.

If you have the right tools, you can do these tests, but reading the fault codes from all the systems may display a code that points you in the right direction.

How to 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. To read and clear BMW codes from various modules, you will need a BMW scanner such as Foxwell NT510 for BMW.
With your BMW scanner, perform a full system scan or health report.
 
A good scanner will allow you to perform an auto-scan of 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 as PRESENT or CURRENT.
 
These will need to be addressed. Codes that show as PAST or HISTORY (depending on the scanner) can be erased without any issue.
bmw no start no fuel

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

 

bmw wont start on cold weather

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

The first thing you need to check is the battery. This problem can be due to a battery that's 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.

A BMW may not restart after an accident due to 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 SafeTerminal.

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 of the airbags having to deploy.

You can bypass the BST by reconnecting the cable. It is recommended to replace the cable as soon as possible.

A fault code will also be stored in the airbag module, and the airbag light will stay on. Once you repair or install a new BMW BST cable, use a BMW specific scanner to reset the airbag light.

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, which doesn't allow 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 connected for at least 15 minutes.

This can be dangerous if your battery has short. It can cause your old battery to overheat and, in some cases, even explode.

If your BMW cranks, but it won't start, the problem is often due to one of the 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. There is 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 spark using a spark tester. It will require that you remove the engine cover and at least one of the spark plugs.

Lastly, you will need to check for compression.

This problem is most often caused by a weak battery or a detonated Battery Safety Terminal. 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 replaced the instrument cluster, the car may not start asking for a code.

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

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

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

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

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

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. Also, 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.

High-temperature resistance can increase at poor connections, not allowing enough amperage to the starter.

Older BMWs have a mechanical steering wheel mechanism that will lock the steering wheel if the keys are moved. To get the key to turning or the car to start, you will need to move the steering wheel slightly then turn the key.

Newer BMWs that have Comfort Access with Start/Stop button may also 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 cars.

Newer BMW cars have an electronic steering wheel lock that may malfunction. The problem is often caused due to the low voltage to 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 that's the case, your BMW steering wheel will not unlock when the key is inserted in the ignition. Call your BMW dealer to check if there is 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

This problem is, in most cases, is caused by a partially discharged battery. Charging the battery will 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 may start fine when cold, but if it warms up, it will refuse to start. The car starts fine in the morning. You drive it for 30 minutes or an hour. Turn off the engine.

Try to start the engine again, but now it won't start. Any of the following can cause this problem.

  • Bad Starter
  • Crankshaft Position Sensor
  • Camshaft Position Sensor
  • Fuel Pressure Issue
  • Starter Solenoid
By YOUCANIC Automotive Experts
Nov 2020

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