[Sam Vejvoda]

I have a 2009 328i bmw. If I bypass my telematics control unit with a fiber obtic, could it still drain my battery? I have been experiencing battery drain and I had a SOS light malfunction on my dash along with popping speakers.. I bypassed the TCU and the speakers stopped popping and the light went away. I am still getting battery drain.. can it still cause battery drain if it's bypassed? Also sometimes my car will not work to be jumped… I'll leave it hooked up to another car for 20 minutes and it still won't be jumped. Could it just be a bad battery? My tail lights will also not turn off and my key phone will sometimes not pop out when I push it in and there will be a weird clicking noise. Please help guys I really could use it.

[ctuna]

Why don't you totally unplug the TCU then it can't drain current.
This means disconnecting the main connector.
You can program out the SOS error with Standard Tools.

Check battery Health first always before other stuff is wrong.
Battery life on these is on average 6 years it can be longer if you
use a battery tender.

Other things could be causing your car to not sleep.

If you have aftermarket equipment are you sure that also turn's off.

These cars do no jump easily and you can have all kinds of problems
with a low battery . You need to put a long slow charge on the battery
and see if the symptoms correct.

Also you need a Voltmeter start getting an idea of the true battery voltage.

[Sam Vejvoda]

Originally Posted by ctuna

Why don't you totally unplug it then it can't drain current.
This means disconnecting the main connector.
You can program out the SOS error with Standard Tools.

Check battery Health first always before other stuff is wrong.
Battery life on these is on average 6 years it can be longer if you
use a battery tender.

Other things could be causing your car to not sleep.

If you have aftermarket equipment are you sure that also turn's off.

Can my car function correctly if it's unplugged? Also do you know how to turn off comfort mode? I really appreciate your response.

[ctuna]

You should always make sure you have a good battery and a good alternator
voltage on these before doing anything else.


TCU does bluetooth phone and SOS system in the years whree it's installed
Mine went bad in been it's out of the car for years. Been like that for a few years I did program out
the TCU monitoring in the Kombi (instrument cluster) .
If the car is a 2007 or greater year it may have a Mulf 2 Hi module which allows
bluetooth phone and usb .
BMW has not supported the SOS system in these since phone company's in the
US stopped using 2g.

What do you mean by comfort mode?
Do you mean comfort access?
If you want to be sure it's not receiving signals from the key fob wrap them in tin
foil or put them in metal box that is sealed. (Faraday Cage)


Anything that is and option in general doesn't need to be installed in the car.
Read some of the training pdf's in the following link if you want to understand
how the car works.

[Sam Vejvoda]

Originally Posted by ctuna

You should always make sure you have a good battery and a good alternator
voltage on these before doing anything else.


TCU does bluetooth phone and SOS system in the years whree it's installed
Mine went bad in been it's out of the car for years. Been like that for a few years I did program out
the TCU monitoring in the Kombi (instrument cluster) .
If the car is a 2007 or greater year it may have a Mulf 2 Hi module which allows
bluetooth phone and usb .
BMW has not supported the SOS system in these since phone company's in the
US stopped using 2g.

What do you mean by comfort mode?
Do you mean comfort access?
If you want to be sure it's not receiving signals from the key fob wrap them in tin
foil or put them in metal box that is sealed. (Faraday Cage)


Anything that is and option in general doesn't need to be installed in the car.
Read some of the training pdf's in the following link if you want to understand
how the car works.

I charged my battery to full and I tried to start it and it didn't even turn over. Only the dash lights will light up. I unplugged the battery from the car for about 15 minutes and plugged it back in and now it's ticking but not even trying to turn over… the other day it wouldn't even try and turn over and I unplugged the battery and then plugged it back in and then it started. Any ideas?

[ctuna]

If the battery voltage is above 12 volts and it doesn't turn over the first
thing likely is the starter motor.
If the signal line that tells the starter motor to start switches , and the car doesn't turn over ,you probably
have a bad starter motor.

You need to measure the voltage of the battery .

[Sam Vejvoda]

Originally Posted by ctuna

If the battery voltage is above 12 volts and it doesn't turn over the first
thing likely is the starter motor.
If the signal line that tells the starter motor to start switches , and the car doesn't turn over ,you probably
have a bad starter motor.

You need to measure the voltage of the battery .

Would you not recommend buying an OE starter?