General BMW Mechanical Help sponsored by RM European Auto
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E90 flat battery...now wont start
E90 flat battery...now wont start
trickle charge overnight, those cars absolutely hate low voltage of any kind.
1991 BMW 325i(Current Daily) (S52) I have carburetors, and I'm not afraid to use them! There are always other fish (engines) in the sea (Craigslist) Life is about enjoying the engine you are sitting behind.
If the battery ran down, the residual voltage level may have left the car's electronics in a confused state. The first action would be to fully charge the battery and then disconnect the ground cable for 30 seconds to hard boot the car's electronics. If that doesn't work the car will have to be connected to a BMW diag system to find out why it isn't starting.
The car makes it possible, but the driver makes it happen. Jim Levie, Huntsville, AL
would it need the right voltage to start even tho it was turning over?
It is possible for the starter to turn over the engine when the system voltage is too low for the DME to operate and fire the engine.
The car makes it possible, but the driver makes it happen.
Jim Levie, Huntsville, AL
Hi i left the battery on charge and it was reading about 12.5v,disconnected the ground for 30seconds Had my friend plug in computer but came up no errors.It was a bit temperamental trying to turn over but when it did it just wouldnt start.I cant figure it out
If the battery
was on charge overnight and only read 12.5v a few minutes after the charger was disconnected, the battery is bad and must be replaced. It should have read 12.7v.
The car makes it possible, but the driver makes it happen. Jim Levie, Huntsville, AL
Ok do I need to register the new battery?
I think the battery does have to be registered.
The car makes it possible, but the driver makes it happen. Jim Levie, Huntsville, AL
The car will still not start with a new battery just keeps turning over.Could it have imobilised itself?
Yeah, it's basically resetting the adaptations for battery life.
Do you have access to DIS?
PM me for info on properly working AC and CEL for your S54 or M54 swapped car.
Registering the battery will have nothing whatsoever to do with whether the car starts. This registering just allows the computer to adjust the
alternator charging rate.
Is there fuel in the car?
You're likely going to need to connect the car to a BMW diagnostic computer (ISIS, or DIS/GT1, or INPA), and ask the computers what they know. If the battery went completely dead for a long period, it's possible that the DME and EWS (immobilizer) have lost the alignment for the rolling codes, and will have to be reintroduced, using the above computers.
Had the car in for a full diagnostics... they told me its the ecu needing replaced as they cannot communicate with itI cant understand why this would happen after a flat battery ;(
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This guide will discuss some of the most common problems preventing a BMW from starting and possible ways to troubleshoot or fix these problems yourself.
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 it is cold, the lights and radio may work, but the engine still doesn’t start. Sometimes, your BMW may not even start with
a jump start.
Symptoms
BMW’s 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 showing 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
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, 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 turn over the engine.
The is usually a
problem with BMW with a battery over seven years old or has a parasitic draw problem.
POSSIBLE SOLUTION
Jump Start BMW
Trick Charge BMW Battery
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.
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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, 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 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 a 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 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
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, 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 located at the end of the positive cable that connects 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 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 and replace it yourself.
BMW dealer 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 need to 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 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
Check the spark plugs and coils if your BMW will not start and then dies. Common symptoms of spark plug issues include 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 that all the wire harnesses are connected properly.
Do not swap the wires between ignition coils. Each 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. Tapping the starter with a hammer may allow you to start the engine several times.
Key / Immobiliser / Anti-theft
The BMW alarm system or the key itself may be why your car won’t start. Try locking and unlocking the car several 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 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 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.
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 PAST or HISTORY (depending on the scanner) can be erased without any issue.
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, and the BMW still won’t start. This is because your fuel lines have air pockets.
BMW will not start in cold weather
In some cases, 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 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 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 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
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 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.
The battery is completely discharged or short, allowing the starter to get enough juice to turn over the engine.
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.
This can be dangerous if your battery has short. 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.
The engine is not getting fuel.
No spark at the spark plugs
Low compression
A bad crankshaft position sensor
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 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.
BMW won’t start just clicks
This problem is 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 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:
Disconnect the battery for 10 minutes.
Next, connect the battery.
Turn ignition with one click. Do not turn on dash lights.
Wait 10 minutes. A timer will also show on your cluster.
Start the car after waiting for 10 minutes.
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 an OBC code.
The car will ask for a code when you turn the ignition on. To deactivate this feature, try the following:
Disconnect the battery for 10 minutes.
Next, connect the battery.
Turn
ignition with one click. Do not turn on dash lights.
Wait 10 minutes. A timer will also show on your cluster.
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
Do not park your BMW directly under the sun on hot summer days to avoid this problem. 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.
BMW won’t start steering wheel is locked
Older BMWs have a
mechanical steering wheel mechanism to lock the steering wheel if the keys are moved. To get the key to turning or the car to start, you need to 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 that’s the case, your BMW steering wheel will not unlock when the key is inserted into 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.
BMW won’t start or is making a clicking noise
In most cases, this problem is caused by a partially discharged battery. Charging the battery will most likley 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 cold, but it 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.
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
We hope you find the Why a BMW Won’t Start guide helpful. Check these troubleshooting and repair guides for more help on your BMW.
Do I need to reprogram my BMW after changing the battery?
Apart from the registration procedure, you also have to code your BMW computer. It'll be necessary each time you replace your battery, no matter its specifications - whether your battery is similar or extremely different from your old one.
How do I start my BMW after replacing the battery?
How to Reset BMW Computer After Battery Change.
First of all, turn the ignition key of the BMW car to the accessory position once the lights and radio are on. You have to do this before starting the vehicle. ... .
Again, press the “Trip” button and hold until Reset appears..
Then, press the same button for the third time..
What happens if you don't reprogram BMW battery?
If you don't register it with the car, it causes the car to charge it too much or too little. Older batteries get more charge sent to it than newer ones, so putting a new battery in will cause the car to overcharge it, which prematurely kills your battery.
What is limp mode e90?
What is Limp Mode? In short, limp mode is your BMW's way of protecting your engine and transmission. When the engine or transmission control unit, called an ABS, detects faulty functioning, the malfunction code is stored in the device and is then assessed to determine the severity of the issue.
