C5 A6 2.5 TDi. ECU failure? Help/advice/thoughts please.

[jontawn]

Hi All,

My old man has an A6 2.5 Tdi, had the engine rebuilt sometime back and it was running beautifully. He retired and parked the car on the driveway, there it's been sat for a few months (6 at the most) and occasionally he'd go out to start her up, let it idle for a bit and then move it up/down the drive. Silly old sod let it run out of fuel and short story is he called a local 'mechanic' who came to bleed some fuel through, I mailed over the elsa bleed process' for the alternative engine type, it wouldn't start up despite having loads of fuel in (now half a tank) and plenty of fuel at the rail. I got him to vagcom it later and it's reporting no comms with the engine ecu:

18258 - Powertrain Data Bus: Missing Message from ECU
P1850 - 35-00 - -

Module 01 isn't found at all, I have checked all fuses to the ecu including the ones in the plastic enclosure and all seems tests a-ok.

I have found an ecu for sale and am happy enough fitting it/ adapting/coding it to suit, but the seller won't accept a refund if it doesn't fix the issue (fair enough i suppose).

So, with that preamble, my questions to you knowledgeable folk are:

it's an EDC15 ECU (4B2 907 401 E) does anyone have any suggestions for electrically testing it? (i.e. it's getting a supply voltage and is also outputting the correct voltages)

or does anyone know of an ecu for sale with the possibility of return if it doesn't communicate with vcds? I suspect a 4B2 907 401 x ECU would suit for testing purposes at the least, but wouldn't want to gamble on it at this time.

The car's year 2000, 5 speed auto and quattro (nice car save for the blue dashboard with wood trim!) if you know of one laying about (probably with a sha**ed set of cams)

any help would be really very much appreciated!
jt

[Monkeymagic]

seen this when water ingress into passenger foot well corrodes can bus wires certain modules won't communicate. check drains round battery and brake servo and foot well. everyone always condemns ecu but other than old mk2 golf digi ones and air bag ones never come across it.

[jontawn]

Hey there... thanks for the reply.

it was running before the old man let it run out of fuel, what I suspect is that the 'mechanic' has royally effed something up by following the procedure to force the fuel pump to start. ... however, i would have suspected a blown fuse if this was the case, rather than a goosed ecu.

also, this ecu is K line rather than CAN (as i understand it anyway)

i'd love to be able to put it on a bench, apply power to it and at least try and communicate with it ... but my knowledge is limited and i seriously doubt it's that easy.

if anyone has any suggestions as to testing it in situ ... or whether there are any tools which could be used to assist with diagnostics, then that would be ace.

tia

jt

[Monkeymagic]

i did think it was too old. the fuel pump on these engines is mechanical i don't think they have electric lift pumps. try a new ecu relay. they are a bit of a pig to re start in they run dry