paul-g

I've seen a few threads on it. can I just unplug mine and things will be okay or will it throw a code?

getting high battery drain warnings and read if the IBS goes bad that could drain battery, if I unplug it will that be good or do I need to buy a one wire?

JayArras

You can unplug the IBS and it won't affect anything. If you are still having high battery drain issues after the IBS has been unplugged for a day or so (after you've recharged your battery), you know that the IBS is not the problem. If everything goes back to normal, you can replace it, but it's not critical.

Mine was attached with a small cable tie that I had to snip before I could disconnect it.

tonyb635

Paul, how old is your current battery? It's also possible your car is not sleeping properly and is getting a little grumpy... I know with mine if I park it in the garage and over the weekend I get near it with my keys she awakes. I typically just lock up the car and keep the keys in the house and away from the car on weekends if I am not driving it and this makes a big difference. If your battery has a couple good years on it I would consider just changing it out and ensure you get the the correct replacement. Sure they can test it and most likely the result may show to be ok as happened with me whenI was constantly getting the same error, but after I replaced the battery all was ok. The only thing that will cause that message now is if I am constantly in and out of the car over several days and never drive it I sometime might see it but I think only 1-2 times in the past two years.

paul-g

brand new battery in April and it still under warranty so I am swapping them out today and unplugging sensor I'm going to run like that for a few days or maybe a week if no problem I will spend the $200 for the new sensor

JayArras

Since you got a new battery anyway, before you shell out the $200 for the new sensor, I'd plug it back in just to make sure it wasn't your old battery that caused the problem. If it reoccurs, then at least you know for sure. If you were to change the sensor later, you probably will have to re-register the battery again.

BimmerFan52

^ +1

Even if you have no trouble for several weeks you will only know for sure if it is the IBS by reconnecting it and seeing it cause the failure again.

Replacement of the IBS will not require registering the battery again, but after replacement the car should sit at rest for at least 3 hours in order to allow the new IBS microprocessor to build a state of charge history so an error code is not thrown.

paul-g

agreed guys the one thing i'm trying to make sure by not having it plugged in is to eliminate the possabilty of having something else drawing on battery like the other big issue conv. access handles on doors. if nothing comes up I had planned on plugging back in to see

BimmerFan52

Yes, I didn't mean that you should cut short how long you leave it unplugged. Even two or three months unplugged would be a valid test and won't hurt anything (the DME will default the alternator output to 14.2V in lieu of feedback from the IBS).

Only after you have given it plenty of time to act up again without the IBS should you plug it back in.

JayArras

Thanks for clarifying that. I said "probably" because I wasn't sure.

I'm wondering why bother replacing the IBS then? Save the 200 bucks. But I remember reading on another thread somewhere that not having the IBS will shorten the battery life. Is that true?

BimmerFan52

The two key functions of the IBS are the DME wake-up function and the control of recharge voltage.

After the engine is shutdown the DME takes recent history of the battery SOC (state of charge) it holds and transfers it to the IBS memory and then goes to sleep. The IBS also sleeps, but wakes up every 40 seconds for a fraction of a second to take a snapshot of negative terminal voltage and exit current in order to update the SOC. If something is drawing power and the SOC is dropping the IBS can send a signal to the DME and wake it up. The DME can then force a shutdown of systems (radio, lighting, etc.) that are drawing power. The goal is to preserve enough charge in the battery to enable starting.

During engine and alternator operation the IBS measures the temperature of the negative battery terminal (with the objective of also measuring battery acid temperature). If the battery is charged with an excessive voltage during high acid temperatures the battery can experience excessive gassing, grid corrosion and removal of water in the electrolyte. The terminal temperature sent regularly by the IBS to the DME is used in an algorithm to determine the optimal output voltage that should be sent by the alternator to the system to minimize these side effects of charging and extend battery life.

Incidentally, this optimum voltage can vary significantly between FLA and AGM batteries. An AGM should never be charged with more than 14.6-14.7V, whereas the FLA can safely see up to 15.5V on recharge (again depending upon acid temperature). This is why if you replace your battery with exactly the same type it could be argued that reprogramming is optional, but if you change from FLA to AGM, not registering the battery could lead to very short battery life.