2000 Audi A4 1.8T

Car cranks but doesn't catch
No CEL light when key moved to on position
At first would not communicate with scanner, replaced fuse behind radio and it started working
Only code is a pending P1850 - Data-Bus Powertrain Missing Message from Engine Controller
Fuel pump does not prime, but can be jumped from either fuse or relay
Checked all fuses and relays, all ok
Swapped ECU with another, still no change

Any help would be greatly appreciated, I am almost at my wits end with this problem

 

Also to add, with key on only lights on dash are parking brake and abs. The center display lights up, and the battery voltage meter registers

 

P1850 means the ECU is not seeing the TCU (Transmission Control Module). Apparently the two need to "see" each other before the ECU will let the engine be cranked. Since you said you checked the fuses, that may not be the issue. Could be a relay or something as simple as a loose ground wire. There are a few grounding points in the engine bay. I'd look for those and loosen them up a turn or so, wiggle the wires connected to the lugs on it, and re-tighten them. This will help re-establish a good contact. Regardless, it sounds like an electrical issue.

 

I will check the grounds tomorrow, had enough for one day. Is there a way to test the control modules to see if they are functioning?

 

Anything else I should check on tomorrow while I have the drive to tackle it again? Any ideas will be great

 

So checked grounds today. All tested out with good continuity and low resistance till I got to the drivers foot well. Found one ground that has nothing. Does anyone know what grounds out to that area. There are several ground wires converging there.

 

Ground wire runs through grommet into driver side fender area. Any idea what I am looking at?

 

So, one last update. Went straight to the ECU as that was what everything kinda pointed me to. Found power and ground going into the ECU. Sending it out for testing will update once I find out

 

did this happen all of the sudden? or were you performing some work to the car?