advice sought for an Audi

[The Boss]

hi

Audi A6 2007 model help needed for a friend

he got to his car, opened it, and put key in ignition. nothing..

radio and lights are all that work, no power or recognition.

had it towed to a garage.

they ran a test via plug in comp thingy.. no faults came up and they told him its dead..

anyway, anyone had this experience with an audi.. or merc?

any idea of what it could be.. i spoke to my guy and he suggested it could be body control module.. but he hasnt seen it..

any ideas of what could cause this kind of fault..

cheers

 

[grober]

In modern cars there are fusible links/fuses to protect major parts of the cars circuitry from damage often incorporated into the small black "box of tricks" that forms part of the connection to the battery post- gone are the days of the simple post clamp. My guess is something has gone down.blown in there. In addition to renewing it the problem that caused it should be investigated--- usual thing is poor jump starting technique following a flat battery incident but could be something wrong on the car itself.

 

[Teflonso]

Assuming that it isn't the obvious flat battery issue and he's tried it with both keys then he needs a proper code scan using VCDS. A multipurpose garage scanner won't find a lot of issues.

A dealer will charge for an hour's labour but unlike MB Star, VAG diagnostics is very accessible and there are lots of people with the right kit. Faults versus code are fully documented on the Ross Tech site and solutions are plentiful.

Go to vwaudiforum.co.uk and post the query there. There's a directory of VCDS users by area who will scan it for the price of a pint or maybe even less than that. There is a very active community of people who can roll up their sleeves and dig deep into the bowels of the coding - I found it a bit worrying when I bought a Merc in the knowledge that when anything went wrong I was going to be in the clutches of a dealer or specialist.

The Passat of that vintage sometimes suffered with a problem with the steering column lock/module/key recognition but I don't know if it was the same on the A6. If that does turn out to be the cause then there are some good fixes on the forum that are a lot cheaper than the official one of having a new steering column.

The worst case it that the ECU and/or dashboard cluster coding to the key has been lost, which is a rather pricey and specialist job to sort out if it involves new hardware. A dealer would want the soul of one of his kids to fix it or at the very least, a healthy, transplant-ready kidney

Let us know how he goes on.

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[Deleted member 11979]

Ignition switch?

 

[sinewave]

I'd not be going back to any Garage that just plugs in a cheap Tat Code reader then just declares the Car 'Dead' and then shrugs their shoulders!

 

[grober]

The fusible links unit may be mounted on the battery or close by. This is from an older TT but may help to show what to look for?

 

[grumpyoldgit]

Can't be a lot of help, but I was watching a programme on TV last night about night workers and their nightly duties sort of thing. Anyway one of the people they were featuring was an RAC guy and one of his calls was to an Audi which wouldn't start.
I wasn't really paying that much attention but he diagnosed it as being the 'body control module'. Don't know what he did to fix it, but he was working on something at the back of the engine, somewhere in the centre region. Sorry I can't be more specific.
He did fix it though.

 

[andy27168]

+1 for what Teflonso has said, it really does need to be plugged into VCDS, and a full scan run, from what you are saying from the symptom's one of the control units isn't communicating.
I had an issue with the BCM on my 2007 model A4 Cab after doing a retro fit, and following advice on an Audi forum I disconnected the battery for a few minutes reconnected and all was well. Though I did have to resynch my keys.
If he is within travelling distance of Southampton, I have VCDS and could run a scan for him.

 

[grober]

Many fault code readers rely on an ignition or permanent live feed to power the interface/OBD2 circuitry. Without this they won't function. If any of the main fuseable links has gone and the interface has no 12V supply the car will appear "dead" and no fault codes can be read?

 

[Teflonso]

I've just been through the VW Electrical System and CANbus document for the 2007 Passat, all 62 pages of it. Granted, it's not an A6 but they use a similar platform and nomenclature, so I'm guessing it's not far off. There is no body control module. My guess is that it is some problem on the Drivetrain CANbus. When he gets the scan results, tell him to look out in particular for anything that shows up on any of the following:

• Steering Column Electronics System (CM J927)
• Instrument Cluster (CM J925) which has within it .... CMJ334
• Anti-Theft Engine Disable (CM J334)
• Engine Control Module (J623)
• Vehicle Electrical Systems Control Module (J519)
• Access/Start Authorisation Switch (E415) This one is Passat specific, the Audi equivalent will definately have a different number.

Also, I strongly support Andy's idea of disconnecting the battery, giving it 5 minutes and then reconnecting. It probably won't work, but it's the go-to first fix for any VAG electrical grremlins.

If I read it correctly, the diagnostics conenction control unit (J533) sits on the LINbus so should be separately powered to the Drivetrain CANbus. It suggests that there should be 12V on pin 15 but I wouldn't want to be the one sticking a multimeter probe in there and risking blowing the whole shebang. The electronics are pretty delicate. Like Sinewave, I can't imagine any professional garage finding the diag connector iteslf dead and then chucking the towel in.

It doesn't tell me what each of the fusible links that Grober is referring to serve, other than to say that they are all for components under the bonnet (like starter motor and ECM?). So I suspect it's not the cause but I do hope he's right because it's by far the simplest and cheapest to fix.



p.s. Having looked a bit further, there is a "Disconnection Relay for CANbus (J788)" which is conencted to the Diag Interface box of tricks shown on the schematic. There's no mention anywhere else in the literature so you guess is as good as mine about where it is and what it does. But if this comes up as an error code, shout up and I'll look in some other info I have.

p.p.s. The Passat fusible links are for alternator, power steering, radiator fan and ABS, but they could have different assignments on an Audi.



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