2008 A6 3.0 TDi Tiptronic

[Matt9591]

Hi all I’m having issues with 08 A6 3.0tdi tiptronic.  When starting in the morning I’m getting parking brake malfunction and parking brake auto release malfunction being displayed on the dash but the parking brake releases ok, the car also will not come out of Park when trying the select drive and the PRNDS is not being displayed on the dash. If I sit in the car for about 30mins it will eventually clear itself and and be back to normal for the rest of the day until you leave it for more the 6 hours. 
 

fault codes I’m getting are 

02443 control head 

00446 function limitation due to under voltage

01315 gearbox control module missing message intermittent 

P1626 engine/transmission communication missing message intermittent 

I have replaced the battery,rear calliper motors, parking brake control module and Parking brake switch. 
 

any ideas would be helpful. Thank you

 

[Steve Q]

You've done a great amount of work so far. It the gearbox control module be at fault I wonder? 

[Matt9591]

I’m not 100% sure how I would test that but it is a possibility. I gonna have to put into a garage I think as I’m running out of ideas and skill 😂