Backstory. I picked up my 2001 a4 1.8T almost a year ago with a seriously overheated (melted the pistons) motor. I finally got around to finishing swapping a new used motor. Did the timing belt, water pump, and cam tensioner before putting the motor in. Now I'm trying to start it up and keep getting a 16725 Camshaft Position Sensor (G40) P0341 35-00 Implausible Signal, 01314 Engine Control Module 49-10 No Communication - Intermittent, and 00668 Supply Voltage Terminal 30 53-10 Supply Voltage Too Low - Intermittent. I've verified I've got spark (screwdriver to valve cover) and fuel (based on exhaust smell and pump running). I picked up a couple spare cam sensors and relays from the junkyard to try swapping out. I can feel the 109 relay in the ecm black box actuate when I plug it in with the key on. Any ideas?

 

My concern would be with

01314 Engine Control Module 49-10 No Communication - Intermittent

Not sure but that seems like the main place to start.

 

Ok. I've done some pin checking and found that I have 12+v on pins 3 and 43, 10v on pin 62, and 0v on pin 21. I should have 12v on 3, 21, and 62. Not sure if I should have voltage on pin 43 at all. I'm basinf this off the diagram in this thread. VWVortex.com - AWM ECU pin out?
Unhooking the tan plug pictured takes out the 10v at pin 62. It reads 12+v at the supply side of the plug. Any idea what is supplies? Been trying to dig up a full wiring diagram with no luck so far.

 

It sounds to me like you have a miscommunication between motor and ECU. Namely the ignition side of the ECU.

What did you swap from? There were a lot of VIN splits in the 2998-2001 model years, aesthetic and otherwise. Can you get the VIN or engine numbers from each side?

 

I did get the car running. Intake cam was off by 1 or 2 teeth. When I replaced the cam tensioner it must have rolled it some because I very careful about making sure I had the right number of links between the cams. I charged the battery and then it started right up and the other codes went away and haven't come back.