ViperRunner

Hi everyone,

Want to ask a bit of help from you guys on something..

My car is a 2005 525i M54 engine.

Latelly i've been experiencing battery drainage and it's appearing a PT-CAN communication fault on DIS and errors on IDRIVE of cruise control malfunction as soon as i turn on the ignition!

If i take out the big fuse 7 on passenger fuse box it will sleep as a baby as expected in the 2min time.

There is no issue with the cruise control stalk itself, already tested and replaced that just to be sure, and it's everything ok.

Need to resolve this ASAP because now everytime i get out of the car, i have to take out the fuse 7 so that it wont kill my battery because it wont sleep. :/ I feel ridiculous doing this on a car like this

Thanks for looking!

Best regards

BimmerFan52

Yes, pulling fuse 7 (CAS) will definitely put it to sleep, but also disable the security system (probably don't care if it is in your garage).

If your battery is good (measures 12.5V after four hours rest) and your alternator is doing the job charging (should measure about 14.2V fifteen seconds after starting) then you might try disconnecting the IBS sensor. Early E60s had IBS that were not sufficiently insulated from moisture, and the failure mode after damage is to repeatedly wake the CAS and ECM, and run down the battery by using much more than the normal closed circuit current consumed while at sleep.

Peer through the window and watch the LED next to the gear shift illuminated after an hour with the engine off. If it stays on, or comes back on then disconnect the IBS and see if it go out and stay out. If so then just replace the IBS (about $300).

ViperRunner

Thanks for the quickreply BimmerFan52.

Bust isn't an hour too much?

In the diagnose procedures for checking if the power of the car is ok it says the windows leds should turn off in 2min, if it wont i should be taking modules or fuses one by one, waiting 2min between each.

Do you know the tests i'm talking about?

Then shouldn't the windows switch led go out in 2 min or should it only happen if it has a good ibs? if it has a bad ibs the led will be on forever right? but if it's good will it behave the same way if the ibs is taken?

best regards

e60rider

I was scared, when i bought my car. Thought it had a drain problem, but turned out to be a bad battery. Always used to drive it to autozone to test battery, came out perfect and needed charge. Then 1 day when the car woulnt start, i took the battery out and had it tested. Surely the scanner sad "dead cell". Popped in a new battery, registered myself and no issues for over a year. Also not entirely sure but I know my car sleeps after 15mins (lights turn off earlier but my nav and other disc's stop moving after 15mins).

My suggestion:
1.Start from a battery test, DONT DRIVE YOUR CAR TO AUTOZONE and get it tested. It will more than likely pass since, some battery cell die partially (only able hold charge x hours).Take out your battery and have it tested (take it out when the car isnt able to start and then have it tested)

2. Go to bmw, they charge 80$ for drain test. (i rather throw the money and get it fixed, i find electric drains a pain in the a** to deal with..)

BimmerFan52

I agree with e60rider that the battery could be dying. In the old days with inefficient starter motors, dino oil (higher crank resistance) and carburetors it took a lot more battery current to start an engine. When the battery started to run low, the slow cranking served as a warning that the battery was on the ragged edge. But modern engines start so easily that you can start the engine fine and then 15 minutes later it won't do anything as the battery has crossed the cranking threshold.

But if it isn't going to sleep you will eventually run down the new battery also.

I say keep an eye on it after an hour (or more) because the IBS usually doesn't prevent the CAS from going to sleep. Typically the car first goes to sleep and then the IBS wakes it up repeatedly. The wake up is supposed to be a one-time thing to allow the CAS to close a relay to shutdown power consumers left on after the engine has been turned off. But the damaged IBS will wake the CAS over and over again.