Audi A3 BKD 2007 non start, flashing brake warning and no ECU communication

[Crasher]

You need to check for ignition live (line 15) at pin 18 of the 94 socket plug (the large one) which ultimately leads back to fuse 2 in the dash side fuse board, I have seen these blow due to faulty brake light switches. You should check for ignition on (line 30a) power to positions 3, 5 and 6 (the larger pins to one side grouped and 1, 2 and 4 are the earths)of the 94 socket plug and if nothing, continuity back to fuse 13 in the engine bay fuse board which comes from the relay terminal 87 on the socket marked 2 on the board.

[rocktheboat]

Hi, I’ve finally got around to having another go on this -

Needed to remove the anti tamper screws on the ECU holder

Can you / have you got any more detail regarding the pins of the ECU plugs ? I know you’ve said the numbers but have you a picture or are there numbers cast into the housing ?

Really want to get the the bottom of this and really appreciate your help

[Crasher]

There are tiny numbers moulded into the receiving case of the ECU which you have to reverse in your head and look back at the plug to use, or on the reverse of the plug, when stripped down, the numbers are also moulded in but to view any of these I have to use two pairs of glasses and a watch makers magnifying glass, a consequence of getting old. This is why VAG insist on using plug in break out boxes which plug into the cars harness and then into the ECU, giving easy measuring access but these are rare, expensive and difficult to find so we all have the struggle so BEWARE, it is VERY easy to strain and damage the plug pins and they are awful to replace.