Telematics control unit bypassed causing battery drain?

Sam Vejvoda · 10-27-2022, 04:03 PM

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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.

CnSky · 10-27-2022, 06:22 PM

It's your battery these cars go nuts when voltage is too low.

Check the 2 (or 3 of it's a G31) batteries and replace as necessary.

CnSky · 10-27-2022, 06:31 PM

You will likely need to change the SOS battery also as they tend to die when the main batteries can't charge them as it's also low.

Sam Vejvoda · 10-27-2022, 07:14 PM

Quote:

Originally Posted by CnSky

You will likely need to change the SOS battery also as they tend to die when the main batteries can't charge them as it's also low.

The SOS light went away when bypassed the TCU. Do you guys know why my car wouldn't jump.. one time I drove it an hour and went into the store for 20 minutes and came out and my tail lights stayed on and my car wouldn't even turn over… I left it for an hour and came back and tried starting it again and it started right up… I'm so confused lol. Could it be a bad cell? My key fob sometimes also doesn't want to come out properly.

ezaircon4jc · 10-28-2022, 09:32 PM

Start with the simplest solution. The battery's been drained to the point it will no longer accept a charge. Find the parasitic draw and replace the battery.

CnSky · 10-31-2022, 12:25 PM

Change your battery and all the strange stuff will go away.

That's all that's wrong.

The SOS battery will fail after main battery fails as it is charged from the main battery and it disables certain devices if it voltage is too low including SOS battery charging.

Light went out as you bypassed the unit that tells you it's low.

10-27-2022, 04:03 PM	#1
Sam Vejvoda Banned 3 Rep 56 Posts Drives: Bmw 228i Join Date: Oct 2022 Location: Florida iTrader: (0)	Telematics control unit bypassed causing battery drain? Featured on BIMMERPOST.com 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.
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10-27-2022, 06:22 PM	#2
CnSky Major 330 Rep 1,028 Posts Drives: BMW 530E 2017 Join Date: Aug 2013 Location: Ireland iTrader: (0)	It's your battery these cars go nuts when voltage is too low. Check the 2 (or 3 of it's a G31) batteries and replace as necessary.
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10-27-2022, 06:31 PM	#3
CnSky Major 330 Rep 1,028 Posts Drives: BMW 530E 2017 Join Date: Aug 2013 Location: Ireland iTrader: (0)	You will likely need to change the SOS battery also as they tend to die when the main batteries can't charge them as it's also low.
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10-28-2022, 09:32 PM	#5
ezaircon4jc Major General 4451 Rep 5,337 Posts Drives: 2019 540i M Sport Join Date: Jan 2015 Location: San Diego iTrader: (0)	Start with the simplest solution. The battery's been drained to the point it will no longer accept a charge. Find the parasitic draw and replace the battery.
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10-31-2022, 12:25 PM	#6
CnSky Major 330 Rep 1,028 Posts Drives: BMW 530E 2017 Join Date: Aug 2013 Location: Ireland iTrader: (0)	Change your battery and all the strange stuff will go away. That's all that's wrong. The SOS battery will fail after main battery fails as it is charged from the main battery and it disables certain devices if it voltage is too low including SOS battery charging. Light went out as you bypassed the unit that tells you it's low.
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