2000, Y, A6 2.5 TDi AKE. Engine won't start & VCDS won't connect to 01

[jtonthebike]

Hi all,

Looking at my dads A6, it ran out of fuel and a 'mechanic' came to 'fix' it ... short story is there is now fuel at the rail and all seems happy (even if that bit isn't working, i have a bigger issue). I can't get my VCDS cable to connect to the engine ECU. It will connect to all other modules without issue and the other modules report:


18258 - Powertrain Data Bus: Missing Message from ECU P1850 - 35-00 - - I have checked the fuses on the side of the dash, the fuses in the ECU plastic enclosure ... I don't have a wiring diagram so am shooting in the dark a little. All I can see have tested correctly. I haven't tested the relay yet (will be doing that in just a mo) I have disconnected the battery and in turn the ECU, opened it up and can't see anything immediately visible (using a wrist strap for esd protection) which would indicate a blown unit, nor does it smell as such.If it needs a replacement ECU i can code it in no probs, I'm just after some additional advice on how to proceed with testing/diagnosis.Any help would be most appreciated.cheers,JT

[PaulF2.5TDi]

Was the car cranked over and over trying to start it?

If so, the battery voltage could have dropped too low. Most electronics can deal with NO volts, but LOW volts can leave some parts of the circuit trying to work whilst others are still not powered.

It could be worth disconnecting your battery for 20 mins or so, then trying again to see if things have reset.

[jtonthebike]

Hi there.

It's been disconnected for 40+ mins while I removed it from the vehicle (battery disconnected) the battery is/was on charge during this time (trickle charger) and the vehicle cranks over without any hesitation.

I had hoped it would be something as silly as a duff fuse that appeared ok, however, each one has now been electrically tested. Then my next hope was a simple reset, which was done during the ecu removal - so it's definitely had power removed for quite the period of time.

Does anyone have any thoughts on testing the relay '209' located in the ecu plastic enclosure? or perhaps what/where to check to ensure there is correct voltage being not only supplied to the ecu but coming out of it? i can't locate an electrical diagram and i'm pressed for time (i live 4-ish hours away) so am trying to do as much as possible.

For a laugh, I spoke with Audi who wanted ... £1300 for a new ECU. It makes paying £100 for one seem most reasonable. I am tempted to source one from Germany (ebay.de) and have it shipped over as it'll be cheaper and I can code/carry out the appropriate adaptations to suit the vehicle here.... though that would mean a repeat visit to the Motherland to fit/install it.

I'd really like to be able to confirm that it is the ECU before I splash out as most places won't offer a return - despite my offering a reasonable % for allowing the fitting of it to test.

thanks for the reply PaulF2.5TDi

JT

[PaulF2.5TDi]

I would hold off replacing the ECU just yet 1 18258/P1850 - Powertrain Data Bus: Missing Message from ECU from RossTech, and a link to the Tech Service Bulletin referenced vw.tb.01-07-54 ECM do not Replace For These DTC's.pdf. (I haven't read the TSB)

Both say do not replace the ECM.