Author Topic: Audi A6 Airbag control unit repair  (Read 2545 times)

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Offline den

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Audi A6 Airbag control unit repair
« on: August 28, 2017, 09:31:24 pm »
Hi everyone.

I need your help with the following problem.
There is an error in my Airbag control unit (Bosch 4B0 959 655 G), which says that it is defective. The error cannot be erased - it is designed in this way. What I have found on internet (the reason) is the following - these control units (CU) have an internal bug. The CU makes a self-test in the first few seconds after ignition is switched on. If during this time supply voltage drops - it marks itself defect. The thing is that this situation is very common - during start attempt with an empty battery you have all sorts of voltage drops. This is exactly what happend to me - started with an empty battery without waiting few seconds till the test completes.

Common solution - replace the CU. But this is expensive and ineffective - the CU is fine after all! So the question is - how can I solve this with uncommon methods. Below are a few photos of the CU. I have found the following - two upper microchips are unimportant to this problem. Lower left is an "airbag control driver", or something similar. No idea what it really means. The middle one is a microcontroller. What is the right one I could not find - maybe it's EEPROM, where the errors are saved? I could not find datasheets for any of these devices.

Main question is - how could I (we) attempt to solve the problem; Erase the error somehow - how? Correct the code - how to connect to the microprocessor? Please give me a direction - what to look for, where to start, because I feel this is too complex to start from 0 without any help.

I have: basic knowledge in electronics; DMM and scope; "The art of electronics"  :D

And thanks for reading to the end.

Den

Microchips
Left: Bosch 30376 0103
Middle: National Semiconductor CR16MFR544EAC
Right: Bosch T459128701
Links to pictures (OneDrive)
https://1drv.ms/i/s!Ahv4tx0RVekCifYMM1FR5A-Q1zOHmA
https://1drv.ms/i/s!Ahv4tx0RVekCifYQsWwaEtfo0dqrSA
 

Offline Naguissa

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Re: Audi A6 Airbag control unit repair
« Reply #1 on: August 28, 2017, 11:20:57 pm »
Change the CU. An learn: never EVER ignite all systems simultaneously. It is, wait 1-2s between electric power on and start engine.

My brother has same problem when pick my car, resulting in ABS light going on.

Enviado desde mi Jolla mediante Tapatalk


Online sokoloff

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Re: Audi A6 Airbag control unit repair
« Reply #2 on: August 28, 2017, 11:30:00 pm »
Here's a video that might give you some clues. It's a bit of a shill for the guy's service to do it, but may give you enough to get started.

 

Online sokoloff

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Re: Audi A6 Airbag control unit repair
« Reply #3 on: August 28, 2017, 11:31:43 pm »
Several related videos come up as well, so poke around.
 

Offline ovnr

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Re: Audi A6 Airbag control unit repair
« Reply #4 on: August 29, 2017, 01:09:23 am »
I really wouldn't poke that beast. It'd be somewhat inconvenient if it suddenly set off the airbags while you were driving.
 

Offline den

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Re: Audi A6 Airbag control unit repair
« Reply #5 on: August 29, 2017, 06:17:13 am »
Thanks!

The guy in the video just promotes his workshop, like "it's too hard, let me do it for 50 bucks". Found another video, where one guy does the thing, but unfortunately for Toyota, meaning I cannot be sure his method will work for me.


So the questions are open - how do I access the EEPROM? Can anyone give a tip where to find datasheet/description of the EEPROM chip? Or at least confirm that the lower right chip is actually EEPROM.

Den
 

Offline IanMacdonald

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Re: Audi A6 Airbag control unit repair
« Reply #6 on: August 29, 2017, 06:31:18 am »
If you can prove the fault is caused by a low battery and nothing else, this would seem to be a critical bug in a safety system. In which case the manufacturer ought to recall the units, regardless of age.
 

Offline Brumby

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Re: Audi A6 Airbag control unit repair
« Reply #7 on: August 29, 2017, 06:58:45 am »
Call me paranoid - but I get uncomfortable when discussions involve playing around with primary safety systems in motor vehicles.

Even if you do succeed in "clearing" the fault - how do you know you haven't affected something else?
 

Offline blueskull

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Re: Audi A6 Airbag control unit repair
« Reply #8 on: August 29, 2017, 07:22:42 am »
The video pointed out a good use of air bag EEPROM tampering -- to wipe out evidence after a crash. Besides, I see no reason to tamper with an air bag controller. The risk makes it doesn't worth it.
Air bag controllers use special capacitors and IC mounting methods as well as footprints to make sure it can handle the most Gs even if other systems in a car fail, and this is for a reason.
If the system has already been subjected to a high G impact, the reliability may be lowered to a dangerous point.
 

Offline max_torque

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Re: Audi A6 Airbag control unit repair
« Reply #9 on: August 29, 2017, 11:47:00 am »
It seems somewhat unlikely to me that the system will disable itself on a single low voltage brown out event?  (especially as i has a massive ride through cap on it, that is designed to fire the bags even if the vehicle supply has been disrupted by the impact).
 

Online Jeroen3

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Re: Audi A6 Airbag control unit repair
« Reply #10 on: August 29, 2017, 12:04:18 pm »
Did you check if there are any recalls for your A6 model?
 

Offline den

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Re: Audi A6 Airbag control unit repair
« Reply #11 on: August 29, 2017, 12:45:59 pm »
OK, I just understood I forgot to mention the vehicle is from 2001 =).

If you can prove the fault is caused by a low battery and nothing else, this would seem to be a critical bug in a safety system. In which case the manufacturer ought to recall the units, regardless of age.

Good idea, but for that I need to get inside the damn thing.

Call me paranoid - but I get uncomfortable when discussions involve playing around with primary safety systems in motor vehicles.

Even if you do succeed in "clearing" the fault - how do you know you haven't affected something else?

Well, now airbags are not working at all. And there are a lot of other not very safe things in such an old car.

The video pointed out a good use of air bag EEPROM tampering -- to wipe out evidence after a crash. Besides, I see no reason to tamper with an air bag controller. The risk makes it doesn't worth it.
Air bag controllers use special capacitors and IC mounting methods as well as footprints to make sure it can handle the most Gs even if other systems in a car fail, and this is for a reason.
If the system has already been subjected to a high G impact, the reliability may be lowered to a dangerous point.

Yes, I want to wipe out crash data. And go to jail for evidence concealment. Because it's fun this way, and I don't have 50 bucks. Also I cannot destroy the thing. Genius plan.

It seems somewhat unlikely to me that the system will disable itself on a single low voltage brown out event?  (especially as i has a massive ride through cap on it, that is designed to fire the bags even if the vehicle supply has been disrupted by the impact).

I know, this is just something I've found on internet, and it kinda explains why the error is there in my case. It really appeared after winter, when I once had an empty battery.

Did you check if there are any recalls for your A6 model?

It's an old car, but still - never found any information on such recalls.
 

Online Jeroen3

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Re: Audi A6 Airbag control unit repair
« Reply #12 on: August 29, 2017, 01:40:53 pm »
Did you check if there are any recalls for your A6 model?

It's an old car, but still - never found any information on such recalls.
Ask. My 8 year old car is going in for a recall on the airbags.
 


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