Is your BMW not starting and not cranking over? If you’re one of the many BMW owners that are looking for ways on how to fix a BMW No Start, No Crank, stay tuned. For most people replacing batteries that are still good is often the quick and unnecessary first thought that only leads to more frustration. Diagnosing a no start a BMW can be expensive and the repair bills can add up quickly. I’m going to show how to diagnose your BMW’s starting issue with simple tools and in very little time.
Most BMW owners have never heard of an IBS. You are probably asking yourself what is an IBS? You can locate the IBS unit on the negative cable that’s connected to your battery. The battery on most BMW is normally located in the trunk. On the negative battery terminal, you’ll see a couple of wires of which one runs to the (+) positive side while the other one runs into a nearby wiring harness. The little black box on your negative battery terminal is the Intelligent Battery Sensor or IBS for short.
In this article I will share some ways with you, so, you can quickly diagnose the real cause of your BMW’s mysterious no start no crank situation.
A no start, no crank is when your BMW’s motor does not turn over when you attempt to start but the main dash is getting power. There could be many reasons for your BMW not starting and below are the most likely causes as long as you have a properly charged battery. If you like to see the video for this article, play the video below:
Have you made an attempt to find out why your car isn’t starting?
Let’s begin by finding out the facts about Intelligent Battery Sensor or IBS
The BMW IBS or Intelligent Battery Sensor is an electronic or mechanical device connected to the terminal of the negative battery directly.
It contains microprocessor used to measure and monitor a lot of battery conditions like a Terminal voltage through measurement from the B+ to Ground, Battery acid temperature through the integrated temp sensor, charge or discharge current through the integrated shunt resistor.
It is able to withstand up to 105°C of thermal load due to battery acid chemical effects.
Disconnecting your car’s IBS may cause your car battery’s shortened lifespan.
Here are some steps you could do to fix the problem:
Locate the battery which in late model BMWs is often found in the rear truck to the right behind the carpeted trim. Once you locate the battery, remove the negative battery terminal using a 10mm socket. After the negative battery terminal has been removed unplug the small harness from the connector. Once the IBS connector is unplugged, reinstall the negative battery terminal. Tighten the nut of the battery terminal before you attempt to start the vehicle. A loose battery terminal could cause a lot of electrical problems. Once the IBS is disconnected, proceed with starting the car. Many people have reported driving with IBS disconnected for a long time and have not experienced any further issues. If you’ve been getting a no start, no crank situation and can’t figure out what it is, try starting your car with the IBS sensor disconnected.
Other possible reasons for a ‘no start’ on BMWs, some of the time, is when water runs down the fuse panel and causes poor connections in many of the fuses. The fuses might look good from outside but there is a strong chance that they may have rusted contacts in the main rear fuse panel. You’ll want to go ahead on checking all of these fuses to make sure that the starter and all needed systems are getting power and are able to communicate with one another.
The Starter is really tucked away under the intake manifold but there is a little cheat if you want to avoid removing your intake manifold just to test the starter. As you’re standing in front of your BMW, with the use of a flashlight, you will notice that you can actually see the starter toward the rear of the motor through the intake manifold. With a few simple tools, I’m going to show how to test your BMW starter without removing any parts. Once you locate your starter under the intake, you will see two terminals. Use a long tip screwdriver and test light that has the ability to detect a ground (–) and positive (+) 12-volt signal. You will need to lower long screwdriver through the intake to lower contact large mesh copper wiring.
Reminder: The starter side will always be hot while the solenoid side will be negative until the ignition sends a signal and turn it hot in order to engage the starter.
Have the long screwdriver tip to the bottom contact, using a test light would indicate a negative signal on the bottom contact. If you touch the bigger terminal, you’re going to get a positive all the time which is normal. Next, use the screwdriver tip and make a connection with the big wire mesh to do a quick test. Have a helper inside the car while you stay outside, still holding the test light and screwdriver perpendicular with each other. Ask your helper inside the car to crank the motor while you keep the screwdriver and test light in the same position. Make sure the screwdriver does not move. When the starter gets the signal to engage, the test light will show a positive signal for a second. If you are unable to detect the a (+) positive signal, then, you’ve got yet another issue in your hands. Some other system is causing your vehicle’s ignition system not to send a signal to the starter to engage. That’s how you test the starter on your BMW.
Other possible causes of a ‘no start, no crank’ could be located under the spare tire, the white module under the spare tire can cause a rapid discharge message and cause havoc on your electrical systems. Proceed to remove your spare tire cover. You’ll notice rust where water has flooded spare tire well. Usually, people leave the trunk open during the rain or there could be a leak. Under the spare, you will see a white module which is prone to failure from the water damage. You’ll need to replace this and the wire harness as well if you notice any rust on the connection contacts of the white module. Make sure that you get the same exact unit. Check the part number to confirm a match, if not, you might have to program it since it might be programmed to a different vehicle. When the module under the spare tire gets damaged it will normally pop the fuse, too. Leaving this repair undone could cause more erratic electrical problems and can really shorten the life of any battery.
Some other reason you may be experiencing a ‘no start’ on your BMW is the positive battery terminal. There is a physical break that will occur on the positive cable that runs from the battery to the starter. This safety feature is called Battery Safety Terminals (BST), most of the time after an accident the BST will get activated and break the positive cable contact. In a way, it’s like a mini explosive attached to the positive battery terminal designed make your BMWs immobile after an accident. Because of this undetectable hairline break in the positive cable, lots of BMW owners have been ripping their BMW’s apart to find out why their vehicle isn’t starting. Thus, causing a lot of unneeded damage to the vehicle.
If you’re still unsure why your BMW is not starting, go to the positive jump port under the hood. At this Jump port, you should have a constant 12-volt signal. Note: The jump port serves as the middle point between the battery and the starter. The positive signal from the jump port leads straight to the starter. If you’re still not getting any power up here, you may an issue with your BMW’s Battery Safety Terminals (BST). You can bypass this temporarily to start your BMW by using some jumper cables. You will need to only connect the Positive battery terminal to the front jump port under the hood which is marked by a red cover on most of the late model BMWs models. Make sure you’ve got a good grip on the positive battery terminal with the jumper cable as you attempt to make the connection to the jump port. Once the connection has been safely made, make an attempt to start the vehicle. If your vehicle starts, you can confirm that BST is causing the no start. Avoid driving while the BST is damaged.
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