1995 2.6 ECU wiring diagram

Posted: Mon Mar 07, 2011 11:48 am

Does anyone have a 1995 A6 wiring diagram as I am trying to fix my instruments as the tachometer, coolant temp guage and air con don't work and I also have a constant oil warning light. I think it is just a simple broken wire but I need to know where to start as it is driving me nuts.

Thank in advance to any help given.

Matt

Posted: Mon Mar 07, 2011 5:14 pm

I'll have a look in my bentley manual tonight (it's at home) and scan the relevant pages... I also think the haynes has a generic version in the manual

Posted: Mon Mar 07, 2011 10:18 pm

Thanks BladeRunner.

Posted: Mon Mar 07, 2011 10:18 pm

Lets hope it is something simple.

Posted: Wed Mar 09, 2011 10:25 am

Right, it has turned out that the new instrument panel I bought was a duff item (as I was told that it was the problem) and so will be going back. I still have no tacho/rev counter and no air con as well as the oil pressure warning but I am told that it could be the RPM sensor feed as it goes to all those systems. Does anyone know how to check the sensor? Also where is my engine ECU?

Posted: Thu Mar 10, 2011 12:11 am

found my bentley manuals will scan the pages tomorrow at work Cool

Posted: Sat Mar 12, 2011 11:49 am

I have spent hours searching and found that everything works from the junction board in the passenger foot well to the instrument/climate control so logic dictates that I have a break in the wire from the ECU to the junction board/connector or my ECU is not outputting a signal.
Anyone have a diagram of the layout of the pins for a ECU part number 4A0907473D??

Thanks

Posted: Tue Mar 15, 2011 5:00 pm

Finally found the pin layout for my ECU. Sorry it is in German but you can work it out by using the sensor G numbers quite easily.

Newbie Joined: Dec 06, 2011 Posts: 2

Hi, I`m glad someone found a pinout of the 2.6 ECU. Though this thread are a couple months old, where on earth did you aquire this??

Inexperienced Joined: Apr 03, 2007 Posts: 31

Help

Short story:
I want to trace/check wiring from my Megamos IMMO1 box to the ecu. I started (maybe the hard way), by removing everything in my way (dash, console etc) and am working the wiring back but it's getting a bit tight for access. So I looked to the other side of the car to investigate the wiring looms where they may come into the ECU.

I only have a voltmeter so is there any way of identifying where the five wires go (I think I can see two of them 'Connecting Station II/position #7'). See the photo with the white box. I am thinking of just running a bypass on each wire to see if that corrects the fault (details on that in the long story)

Long story:
Car (1995 A6 2.6Auto, UK spec) starts normal, cuts out 3 seconds later - NO IMMO flashing light. Problem has been intermittent for 2+ years. Over the years VCDS showed 'engine start blocked by immo', 'key signal too low' and 'coil reader signal low'.

Have replaced ignition switch, wiring loom from reader to immo box, reader coil, ignition barrel, key, transponder and was fine for a year. Now problem is permanent - no start. If I remove the transponder, car starts/stalls and the IMMO light flashes as it should (suggests reader coil/loom/key is working).

So having replaced all the other parts, my process of deduction is that there is an issue between ECU and Immo box (as if it cannot hear what the immo is saying)

Posted: Sun Jan 08, 2012 5:32 am

Have you tried the old trick of unplugging and plugging-back-in the immobiliser wiring plugs? The terminals oxidise over time due to galvanic issues with differing terminal materials on each side of the plug

This is the trick on A4's...

Sorry if a bit obvious!

Inexperienced Joined: Apr 03, 2007 Posts: 31

hi, I've not actually tried that as a first resort but have many times dismantled all the components/removed the wires from the connectors. But if I still have problems when I put it all together I will give that a try as it's easy enough to access, thanks for the tip...

Inexperienced Joined: Apr 03, 2007 Posts: 31

I tried the unplug/replug tonight and no luck there. I ran a bypass on two of the five wires (one goes directly into the ECU at B6) but same symptoms.

What gets me is the car has been stationery for three weeks, I reconnect ECU etc and starts up and runs ok. Then when I shut-off and re-start, it cuts out. After a few more attempts over 10 minutes I get it restarted.

I would have thought bad wiring/connects to be more consistent than that, could this be more a problem with ECU/Immo chips or k-line (ie more the signal than the carrier).?

Posted: Sun Jan 08, 2012 10:35 pm

Your car is displaying all the obvious symptoms of having the immobiliser shut down the engine (regardless of the light flashing or not).

Having replaced the transponder, reader coil and wires, the problem must lie within the components - either the Immobiliser or the ECU.

I'd pull the immobiliser apart and inspect the board for dry solder joints. Even see if you can find someone to test it on a work bench.

Then do the same to the ECU. There are various places around that can do ECU repairs, and these days (provided you can locate the correct part number) you can even pick up the whole ECU relatively inexpensively. (VCDS should be able to code the immobiliser to it)

I'd be loath to replace the immobiliser unless it was cactus, as your transponders are then useless as well and would have to be replaced.

One alternative (though I'm not sure if VAGCOM/VCDS is capable of doing the required changes) is that US market cars of this era did not have their immobilisers active (or even fitted?). So there should be some way of deactivating the requirement to talk to the immobiliser before starting the engine.

Inexperienced Joined: Apr 03, 2007 Posts: 31

ok, agree that's the best route - I sent my ECU off to a specialist a year or so ago to check and they couldn't diagnose it (apparently Hella ones are a bit tricky).

There are loads of immo boxes on ebay.de very cheap and if I can find one with a known PIN code I am guessing I could get a new transponder coded to it - for less than €40 I'd know whether the immobiliser itself is the issue (ECUs for auto boxes I've seen are a couple of hundred so more of a last resort)..

Posted: Mon Jan 09, 2012 6:25 pm

Obviously if you do choose to replace the immobiliser, see if any of them are offering the transponder chips as well.

Inexperienced Joined: Apr 03, 2007 Posts: 31

that would be ideal but the only options I've seen are to buy keys/locks and the immo unit which pushes the price way up.

I can get a new ID13 chip for under €10 so I need to find out if VCDS will enable me to match a fresh/unused chip to the car (not sure if chips need to be programmed first??).

Inexperienced Joined: Apr 03, 2007 Posts: 31

Found the wiring details for the immo box on this very site!!

http://www.audifans.net/ftopict-17196.html

does anyone know if I swap the immo 1 box/transponder, do I need the skc to adapt the ECU or is it plug and play?

found a few breakers who've got the immo and a key

thanks

Posted: Sat Jan 14, 2012 12:58 am

From what I just read in the long post of that thread, an earlier Immobiliser (which yours should be) only needs VAGCOM (VCDS) to adapt.
Even non-encoded transponders (ie new ones) can be coded using VAGCOM apparently, though how I'm not sure.

The SKC is only needed on later immobilisers with scrolling code keys, or if adapting an immobiliser to a non matching key (though not vice-versa from what I understand)