VAG fault code 00438

[kevsmith]

Hi, I have a b8 2.0 tdi 2009 quattro avant.
My fuel gage wasn't working so I changed the sender unit on the side of the pump in the tank, that didn't work so I acquired a used one to try, still not working, thinking maybe a bad connection somewhere, has anyone got any ideas, I have looked at threads but none I can find go into the wiring and checking it ect, thanks in advance

 

[kevsmith]

Anyone?

 

[spartacus68]

The original sender unit, was it new from Audi? That should come with 2 year warranty. Any other details from VCDS in terms of this error? Take it you've checked fuses, etc.

The 00438 error tends to be associated with the fuel gauge sender (G169) I did read one or two people identified broken wiring as culprit. Anything obvious when you are under the back seat? I wouldn't even know how to go about a continuity test, as you probably need access to a wiring diagram.

 

[kevsmith]

Hi, unfortunately no it was a private sale so also inherited the problems as well some of which I have fixed others I'm stuck on lol, the units in the tank look OK, the sender I bought was a ebay jobby, it seems that the sender has a mind of its own, by this I mean sometimes it works other times more often than not it doesn't show anything on the fuel gage with an error on the dis, when scanning the car not with vcds as I don't have access to it, I use a vident scanner but it gives me detailed report as to where the issue is, ie g169 or 00438 so I guess it might be a case of chasing wires for obvious breaks, with out a wiring diagram it is going to be a task

 

[spartacus68]

Not sure if this is any use. This is PDF wiring for CAGA engine (and others), second last page. Shows route from fuel sensor and sender to fuel guage. Importantly also shows earth locations.
https://www.audi-sport.net/xf/attachments/b8-caga-engine-wiring-pdf.83832/

Ideally, after lockdown eased if someone close with VCDS can help it may add something to the mix.