BMW Won’t Start After a Battery Change

You have already endured the hassle and expense of a battery replacement for your BMW, but now your BMW won't start after a battery change.

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Maybe your BMW wouldn't start before the battery changed, and you assumed a dead or damaged battery was the problem. But the problem still exists, and your car won't start. You could also be on the other end of the podium where you did a routine battery change for an old battery, and now your BMW won't start after the battery change. After solving one problem, you now have a new problem.

Don't despair; this article will explore why your BMW won't start after a battery change and what you can do about it.

Common Reasons Why Your BMW Won't Start

Before we blame everything on the new battery, let's first take a look at the most common reasons why your BMW won't start after a battery change.

• Electrical Problems

Fuses are often the problem when it comes to a car that does not want to start. A blown fuse is located in one of 3 areas:

• In the Engine Bay
• In the Trunk of the car
• Underneath the dashboard

Remove the fuse and check to see if it has blown by visually inspecting it. Some of the most common fuses to check are:

• The Starter Fuse
• The Alarm System
• The Fuel Pump Fuse
• The Immobilizer or Security Fuse
• The Main Relay

• Worn Spark Plugs

One of the reasons your car will not start could be due to worn spark plugs. Replace the spark plugs and see if the car starts; if not, there is one more check that you can do.

Check that all the wire harnesses are correctly connected. It is important not to swap wires, though. Each ignition coil must be connected back to where it was disconnected from.

• Faulty Starter Motor

A faulty starter motor will prevent the engine from turning over. The most common symptom of a damaged starter motor is when you turn the ignition, and nothing happens.

If your starter motor or solenoid has burnt out, then when you try to start your BMW, you will hear no engine sound at all or a loud clanking noise.

Often when a car does not start, the problem lies with the battery or the starter motor. If you have changed your battery, then there are two possible causes:

• The battery and the starter motor have not been properly connected.
• The starter motor is damaged or completely dead. 

• Problems with the Key, Anti-Theft, or Immobiliser

The alarm system or your key itself may be preventing the car from starting. While sitting in the car, try locking and unlocking it several times. If the car still doesn't start, then it may be the key.

Ensure that the key has not gotten wet or been stored in a humid environment as this will cause damage.

Test the key's functionality by trying to start the car with the spare key. If it still doesn't work, there may be another cause.

•  BMW Fault Scanner

If your BMW will not start but the lights and dash switch on, have a look at the fault codes that the car reports.

First, perform a full health report on the scanner. A Foxwell NT510 Scanner is the best option for BMW. Once complete, the scanner will generate a report with codes. You need to focus on any codes that have the status current or present.

• Fuel Problem

A bad fuel pump relay or faulty pump can cause poor fuel pressure, which will prevent your car from starting. Quite often, all that is going on is that the pump relay is too cold and needs to warm up a bit first.

Another problem experienced by older BMW models is a faulty fuel gauge. Your gauge may be telling you that your car has fuel; however, the fuel tank may actually be empty.

•  Engine Temperature Sensor

If your engine coolant temperature sensor is faulty, your BMW will struggle to start or may not start at all. This is common on a cold morning. Should this part come up on the fault code reading, the sensor may need to be replaced.

• Faulty Alternator

An alternator charges a car's battery and provides power to the car's electrical system while the engine is running. If you have a new battery and your BMW still won't start, then you may have a faulty alternator. 

Symptoms of a faulty alternator include: 

• The “ALT” or “GEN” indicator light comes on.
• Headlights are dim or flickering.
• Electrical failure may occur, such as the power windows not working.
• You may hear an unusual rattling noise.
• Car stalls or won't start at all.
• Your new battery is drained. 

A damaged alternator will not charge and will not be able to charge your newly installed BMW battery. When your alternator is not charging, the most common causes are: 

• Worn carbon brushes inside the alternator.
• A damaged alternator.
• A faulty fuse.
• Wiring or circuit issue.
• A broken belt.

Cost to Repair the No-Start Problem

Let's take a quick look at the costs involved in fixing the possible cause behind why your BMW will not start after a battery change.

• Fuses: It can cost you, on average, between $83 and $95 to replace the fuses on your BMW.
• Spark Plugs: These are a bit pricey, ranging from $226 to $342 to replace.
• Starter Motor: As this is an integral part of the motor, the replacement cost is between $400 and $600.
• Key – BMW keys can cost between $300 and $410 to be replaced, depending on your vehicle and type of key.
• Immobilizer – Priced roughly at $100.
• Anti-Theft System – A diagnostics test on the system could be charged from $60 to $110. Replacing the system could cost up to $475.
• Fault Scanner – The Foxwell NT510 Scanner recommended for BMW costs between $139 and $189.
• Fuel Pump – Is priced around $72 to replace
• Temperature Sensor: This part is valued at $50 for replacement.

Sometimes the cost of parts and labor to repair your BMW will exceed your affordability. Instead of being stranded with a car that will not start and you cannot afford to repair it, hand it over to Cash Cars Buyer. They will buy your damaged vehicle as is so you can move on to purchase another car.

If you have gone through the list of possible causes why your BMW won't start after a battery change, and none of the issues seem to be the problem, then you need to reset the car's computer system.

BMW Computer Reset

BMW is a very sophisticated vehicle. Its systems and diagnostics are all run by a computer. Whenever any kind of maintenance is done on your BMW, the computer needs to be reset as well.

Battery reprogramming will occur once you have fitted a new battery into your BMW. Since it is a high tech machine, the car will already know the new battery's specs to modify the charging algorithm.

If you do not program your computer correctly, you run the risk of severely limiting the new battery's lifespan.

As your car's battery gets older, it requires a larger charge to keep the car running. By placing a new battery into your BMW and registering it correctly, you are essentially telling it that there is a new battery that does not require as much charge as the previous one did.

This will help the vehicle know that the battery is new and the computer will not overcharge it, thus damaging the new battery or the integral electrical system that houses all the information.

A computer reset will perform the following tasks:

• It confirms the new battery registration
• It achieves an 80% capacity as a point of reference
• It stores current odometer readings
• Battery statistics such as temperature, voltage, and current are enabled
• Charge levels are deleted

Four Steps to Reset your Computer

1. Turn the ignition key to the accessory position; please note, you are not turning the car on. This is the point just before starting the vehicle where the lights and radio come on.
2. Hold the “Trip” button on the instrument panel until you see a red light come on.
3. Now press the “Trip” button again until the word Reset appears on the screen.
4. Press the “Trip” button for the third time, and the computer will reset.

Once you have all this in place, you should be good to go. 

Which BMW Models Require a Battery Reset?

Any BMW that was manufactured after 2002 will require you to reset the battery on your computer. These models are more electronically advanced and equipped with IBS (Intelligent Battery Sensors), which contain microprocessors.

These processors monitor the charge, voltage, discharge, current, and battery temperature to preserve your battery life, as well as monitor and maintain its performance.