When turning the ignition key, suddenly the car lost all electrical power?

Tiny
CORYMILLER
  • MEMBER
  • 2006 BMW 325I
  • AUTOMATIC
  • 100,000 MILES
When I turned the ignition key, I suddenly lost power to everything, none of the lights work including the dome light and there is no power to anything. I have checked the battery, alternator and all of the connections under the hood and everything is good but nothing works.
Wednesday, August 31st, 2022 AT 11:19 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,526 POSTS
I would remove the battery cables and clean them. Here is a guide to help you fix the problem:

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

Please run down this guide and report back.
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Wednesday, August 31st, 2022 AT 5:40 PM
Tiny
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Battery is only 2 years old, and the cables are in perfect condition. Thanks anyway Ken.

The car key fob battery died and when I went to start the car the dash flashed three times with the key symbol and went dead. The next time and every time since I can't get power anywhere in the vehicle.
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Wednesday, August 31st, 2022 AT 6:07 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,526 POSTS
We try the easiest thing first, so this car has a battery sensor that could be going bad. I would use a test light and when the car loses power so if power is still going through it. Here are some notes on it, if the battery sensor is okay there is a terminal 15 relay that needs to be checked are replaced. Please check the guide and images below to fix the problem.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Note! Do not connect the charger to the 12 V charging socket
The 12 V charging socket is supplied with voltage by the rear power distribution box via relay. This relay drops out after terminal 15 OFF. This means that a battery maintainer connected at the 12 V charging socket will be disconnected from the battery. Only charge the battery via the jump start terminal. Only then can the voltage supply be registered by the vehicle.

Warning! Danger of destruction in event of mechanical strain
Do not introduce any additional connections at the battery negative terminal.
Do not modify the grounding cable. The ground cable also serves heat dissipation.
Do not establish any connection between the IBS and the sensor screw.
Do not use force when disconnecting the terminal cover from the battery terminal:
Do not pull on the ground cable.
Do not place any tools under the IBS to lever off the terminal cover.
Do not use IBS connections as levers.
Use a torque wrench and set tightening torque in accordance with repair instructions.
Do not release or tighten down sensor screw (Torx screw).
Avoid contact between IBS and ground.

Warning! Danger of destruction to IBS and wiring upon battery replacement
The IBS and wiring can be destroyed by mechanical strain upon battery replacement. Therefore avoid mechanical strain.
The size (capacity) of the battery required for the car is coded in the Car Access System (CAS).
Use the battery size (capacity) installed standard upon battery replacement.
Recode the Car Access System (CAS) when installing a battery with a different capacity.
Register battery replacement via service functions in diagnostic system.
Delete fault code entries in the Digital Engine Electronics (DME) associated with battery replacement.
Always proceed in accordance with the repair instructions.

Note: Battery draining possible in spite of the intelligent battery sensor IBS being fault-free.
A battery can be drained (e.g. with lights or radio switched on) even when the IBS functions perfectly in conjunction with power management.

For this reason, only exchange the IBS when there is a corresponding fault code entry!

Let me know what you find.
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Friday, September 2nd, 2022 AT 9:31 AM

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