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Hello,

I have an issue with my Audi RS6. Its a 2003 with 108k miles. It has an intermittent fault that usually happens on start up after being stopped for a long period, over night or over the duration of a days work but it can happen when the engine is still hot.
When you start the engine and gearbox immediately go into limp mode signified by the gearbox display on dash being lit completely.
This can only be rectified by stopping the engine and restarting and will usually clear first time but can take 5 or 6 starts to clear. Once cleared the gearbox and engine are fine until the next random appearance of fault on start up. (sometimes up to 2 weeks, sometimes the next day.)

Currently there is one fault code for the gearbox which is - 18223 Pressure Control Valve 1 (N215) Short to plus P1815 Intermittent.
We have had the supposed solenoid valve changed in the gearbox as one was giving a different reading to the others diagnosed by a gearbox specialist. We have then since had the gearbox wiring loom replaced.
We have had each wire and plug checked for continuity from the gearbox to the loom and into the gearbox ecu.
We have now most recent sent a feed direct from the ignition to the gearbox ecu as we thought it was not getting the start up signal but this has not fixed it.

Any help would be gratefully received.

Aaron Macleod

Could be low ATF. Maybe a faulty TCU given the random error code. Or both.

Or maybe a bad earth on the gearbox loom. Worth checking.

Thanks for the reply. The ATF level is spot on. We also ran a new earth when we fitted the direct ignition feed.
The Faulty TCU is so far the best idea! Do you know anyone who is capable of testing this to see if there is a fault?

These guys are worth getting in touch with.

http://www.bba-reman.com/uk/Catalogue.aspx

Don't know where you're based, but maybe you could try and borrow a known good TCU? It's not a huge job to swap across....

It's always hard to test for intermittent faults.

You might be better off just trying to find one on ebay and swapping it out. I don't think they go for much. And if it's not that then sell it on.

You should use the Vagcom to run the output tests on the gearbox to actuate the solenoids one by one, and see if any generate a code after a few cycles, especially when the car is in the same condition as when the fault occurs. Might not tell you anything useful, but it might.

Might be worth logging groups 6 and 7 to see if any of the solenoids are pulling an unusual amount of current.

Any other codes stored? Other than that one?

Any codes in the engine module?

We know, we've had this fault for long time!

The ebay idea sounds good!

I think that has been tested, but I will confirm that!

There are no more fault codes on the gearbox. There is an engine code for -
17985, right engine mount solenoid valve(N145) open circuit P1577 No signal/No communication.

That fault has been there since May 2013 but the engine mount code has been there since we bought the car in Nov 2011.

Did you ever find the fault for this? mine is doing this and is driving me nuts..?

Just had the exact same problem/fault on my car.. (18223) after reading this thread I thought I'd go straight for the TCU!
Replaced it and has worked a treat.. so far.
It was a 15 minute job and no garage visit. Although you will need vag software in case you have to program the new TCU. Second hand one I bought off eBay was already set up same as my old one, very handy!

How much was the TCU, I had a few issues last year but couldn't find a secondhand TCU. I reflowed a few dodgy looking joints and it's been fine since.

There was a few on eBay but £500-£600?!!! Ended up paying £235 from Lithuania! Chuffed to bits it's worked as it's been an intermittent problem since I bought the car over a year ago.
Wonder what they cost from Audi?

What's the right part number for the TCU?

Here you go...

Hi guys,

Just been reading through this message and thought i would copy a link to my old post looking for help in pretty much the same issue.

https://forum.rs246.com/viewtopic.php?f=2&t=119834

Mines is a little different as the fault only comes up when you turn the key to the first stage and let the check run. i can clear the code (or it doesnt come up when when i click strait to start.

I have been through every cable between the tcu and multiplug, and i know the solanoids are good. i have ordered a new cable for the box and hope to change it out tonight in a bid to eliminate that.

One other fault i have is that im getting a fault (short) in one of the engine mounts. Could these be linked do you think, in terms of they are both short to plus faults?

Would be good if we could bang our heads together (its less fun banging it against the garage wall) and see if we can trueley point point what seems to be spurios.

Cheers

si

Wow. Triple zombie thread.

Shame the OP didn't come back to say whether he resolved the issue. Rule 26 confirmed.

The solenoids almost never fail. It's probably the TCU.

The engine mount is completely unrelated.

Thanks for the update, think I'll bite the billet and go for the tcu then.

Cheers,

Appreciate it