A3 1.6 build

[incognito]

Hi all, I'm building up an A3 for the wife but it is starting to get the better of me. After countless hours of researching and head scratching I have signed up in hope of a little assistance.

To start out I had an 12/07 build A3 with the 1.6 petrol that was damaged when I purchased it. I purchased it for another car which fell through so ended up owning a damaged car with no purpose. It had a front impact but started and drove fine, no issues other than the front damage. 119,000km on the clock and just had a major service including timing belt.

Several months later I get my hands on a 05/07 A3 with the 1.8 petrol turbo. No damage, nice car but destroyed the head after the timing belt jumped.

So I've stripped both cars, completely, to do a body swap. Found out the hard way that the body wiring harnesses are completely different to the two vehicles so that needed to be swapped out as well. Not a lot of fun but got it done.
Everything is swapped from the 1.6 car to the 1.8 car. That includes the full driveline by swapping over complete engine/gearbox assemblies still on K-frames.
I swapped the brake booster, 1.6 had a sensor, 1.8 did not. Swapped the M/C while I was there and also swapped out the ABS module.
Not much under the bonnet was not swapped out.

After connecting the battery for the first time I find the first issue, but not my main one, the secondary vacuum pump comes on and stays on. I disconnect it to worry about that later.
I then attempt to light up the dash and hit the starter. I get a brake fault warning. I have no connection it looks like to the brake pedal switch. I get no tail lights when I put my foot on the brake and the shifter will not unlock from park. Therefore when I hit the starter, I get nothing.

I attempted to manually trigger the starter with the ignition ON, it cranks fine but will not fire.

I've purchased the Elsawin service manuals which is an overload of information but I can not find anything at this point to help this situation.
I have an iCarsoft i908 scan tool but it will not connect to the car. Doesn't matter if I try to do an OBDII scan or by selecting specific components to scan, it wont connect. I am in contact with iCarsoft to try and find out why that is.

I'm thinking I should purchase the VCDS HEX-V2 Enthusiast as it appears to be the best tool to diagnostics but am hesitant to spend the money until I know more. Money and time spent at this point is becoming quite over the top.

To me it is like I have no power going to something to do with the brake system. I put a multimeter on the brake light switch plug and there is current coming from it.
I searched Elsawin to find that fuse 22 on the engine bay panel was the the brake light fuse. I am not getting 12v from it but instead it appears to be earthed out.

When I had to unpick the large plug under the engine bay fuse panel to pass the wires through the firewall I did damage some of the pins in the process. I've removed those that were and soldered on good ones from the donor vehicle's harness. Nothing else at all has been interrupted in that kind of manner.

I've backtracked, checked and gone over and over with no luck. Not having a functioning diagnostic tool is not helping but if anyone has any pointers, I'm all ears and very much appreciative.

Cheers,
Ash

Oh, and one more thing which may be critical, I am in Australia, I do not know if this effects anything at all?

 

[incognito]

After more research and tinkering I was looking into the power supply to the relays. I read that the 458 relay (R1) is the ECU and the 100 relay (R2) is the secondary vacuum pump. Pulling the 100 relay made no difference to the pump wanting to stay on with the battery connected and the key switched off. Bridging the 458 relay made no difference to the cars previous non-running state. But bridging the 100 relay starts the car. Yes!! So I have a issue here. The car started straight up and I once again have brake lights. I was able to drive the car for the first time under its own power. Everything is still pulled apart and in pieces so I still have warnings and faults galore on the dash. But at least at the moment it starts and runs.

Is anyone able to shed some more light on why which relay does what and why they do not exactly correspond to the service manuals description?

 

[incognito]

Got it, yes!!

Murphy's law struck, of course, I had the two identical red/black wires that go to T1 and T2 on the back of the fuse panel, both are the large orange 40amp fuses, I had them back to front. Swapped them around and tada, no more secondary air pump running and engine now starting off the key as it should. So stoked!

Took quite a bit of time of reading flowchart manuals and backtracking wiring but it's done.

The gear shifter is still not releasing out of park but the dash is still in pieces so will assemble it correctly before I start chasing that issue. It might resolve itself in the reassembly.

I have to say, this has been a massive learning curve in German wiring. It's very different to the Fords that I am use to. And even though it has just been myself in this thread, it has helped thinking out loud.