RS2 dies randomly - loosing switched 12v to PIN27 @ ECU

[andersg]

Hello oh the knowledgable S2forum

My RS2 suddenly died on me a days ago. After all the usual checks, I narrowed it down to PIN27 not getting switched 12v. I made a temperary jumper cable from PIN18 (12v supply) and it fired right up. I've tried three different ECU's, all same result. I'm looking for the 12v source for PIN27, does any one know of some scematics? I was hoping it was just a sticky relay I didn't knew existed, but I am afraid I need a new ignition switch...
Here's the pinout:
http://www.s2central.com/motronic_pinout_ABY.html

[4WDrifter]

Check the central locking vacuum pump. There is something inside it to do with the immobiliser I think from memory.
Please don't slate me if this is rubbish.

[prj]

Check the central locking vacuum pump. There is something inside it to do with the immobiliser I think from memory.
Please don't slate me if this is rubbish.

It is

[S2central.net]

Hello oh the knowledgable S2forum

My RS2 suddenly died on me a days ago. After all the usual checks, I narrowed it down to PIN27 not getting switched 12v. I made a temperary jumper cable from PIN18 (12v supply) and it fired right up. I've tried three different ECU's, all same result. I'm looking for the 12v source for PIN27, does any one know of some scematics? I was hoping it was just a sticky relay I didn't knew existed, but I am afraid I need a new ignition switch...
Here's the pinout:
http://www.s2central.com/motronic_pinout_ABY.html

The RS2 has some specific funky wiring around factory immobiliser which do include some additional relays. I can hunt down the correct diagrams - I held those back from public view on the website.

[4WDrifter]

It is

I consider myself suitably slated

[prj]

The ECU is what decides to immobilize something or not. The immobilizer does not affect anything. It just tells the ECU if there is a valid key or not.

[andersg]

Quite ironic about the sentral locking pump, I would have never guessed that. The locking pump went berzerk this morning when locking the car at work, like a horn, just from the back of the car. It stopped when I opened the doorlock with the key. First time that happened.

I have a spare sentral locking pump laying around somewhere, any chance they are switchable? Or maybe the excisting one is fixable.

I thought the immo was in the ECU and was written off with my chipset.

[S2central.net]

Forget the IMMO here guys - if the ECU doesn't get 12V on pin 27 then the engine ain't gonna run anytime soon. I got your PM Anders - I will hunt out the schematic and send you privately latest tomorrow.

[S2central.net]

PM sent - I had them in JPG form already on another machine. There are three relays involved and there is connectivity with the central locking / alarm controller. In the event of an alarm, that controller changes some outputs which trigger the relays to disable certain things on the engine - nothing to do with IMMO-enabled ECUs, key transponders and such - this is old school !

[4WDrifter]

[4WDrifter]

I think this is the pump

[S2central.net]

It is indeed a pump, central-locking unit & alarm controller - V94 in B3/B4 schematic language.

[andersg]

Thanks for all the comments guys, all advices welcome.
i actually do have another pump on the shelf some where. My car is basically two cars merged into one, lots of extra bits on the shelf that surprisingly often come in handy.

i think Paul/s2central.net's schematics will help me fix the problem. Now to just find the time to get in the garage, it's hard to leave the newborn

[andersg]

It is indeed a pump, central-locking unit & alarm controller - V94 in B3/B4 schematic language.

They relays, are they inside the pump?!

[S2central.net]

no no no - you need to understand schematics... First page I sent notates where the relays live but you need a bit of Audi wiring orientation before it all makes sense.

V94 is just the pump / controller unit.
Relays shown 'above the line' are in the main fusebox - in the engine bay.
Relays shown 'below the line' are in the auxiliary relay panel - above drivers pedals

I notice a handful of connectors between the various components of the madcap immo wiring on the RS2 - those will be very well buried in the seething mass of spaghetti cables in the drivers footwell, so you need some strong patience to fork through that rats nest.

It might be worth swapping over the pump if you have an identical spare - V94 is the brains of the outfit on this - the relays are merely helpful minions, but a stuck one will mess things up.