A4 VR6 Conversion to A4 ALH TDI Wiring Harness

Need HELP with wiring harness swap A4 VR6 to A4 Alh TDI , changed engine harness with swap. Do I need change the whole interior wiring harness? Has anyone done this before, could use Help.

I expect that VW still used a common fuse and relay block for the VR6 and TDI mark 4 and they did on the VR6 and TDI mark 3. You'll need to unplug the VR6 AAA engine harness from the back of relay block, but leave the other plugs for the rest of the car alone.
Then plug the TDI ALH engine harness into the back of the relay block.
You'll also need to transfer the relays from the front of the ALH relay block into the recipient AAA relay block. Just because the plugs from the AAA and ALH are the same configuration doesn't mean the wires in those plugs have the same function.

Thanks so much for your reply.I'll give it a try and get back to you.Thanks again

I'm currently doing the same swap. Just pulled the VR6 now I've got to determine if I want to trace every wire coming through the firewall and swap them with the TDI harness or butt splice wires. I've got both complete cars side by side. I realize the cluster, ign. sw., and gas pedal need swapped from the donor car. Any insight?

Still working to get it done

I installed engine harness from TDI with ecu (had emobilizer blocked and egr deleted) plugged in gauge cluster. All connected to the vr6 interior harness, able to start and run engine but runs 4 exactly 2 minutes and shuts down. I havn't been able 2 find both wiring diagrams or the time 2 get it done. Please let me know how you make out

I have a mess of wires but have refrained from cutting anything yet. Trying to sort out and label functions for each but the Bently manual diagrams don't seem all to friendly to me. Sounds like you have anti-theft (immobilizer in VW terms) issues. Did you do a cut and splice of both harnesses at the firewall?