TCM Gremlins - help needed please

[tangerineshep]

Okay,

I think (thanks to VCDS) that I have identified (one of) the problem with my A8.

Perhaps prematurely, I bough a second hand TCM as I believed that it would be a part number swap (4D0 927 156) however I have noticed that the last two letters don't match - is there any relevance to these letters?

In any case, put it in, car went into limp mode and complained that it was improperly coded - tried changing soft coding but it just won't let me. (I could do this as much as I liked with the old TCM - is this where I would need a login?) - Eventually lost me head with it and reverted back to the 'less' broken and original one.

Is there something else that can be done using ross-tech or am I going to be forced to hand over loads of cash for a new one and possibly a dealer coding.

Any help appreciated here.

[Guest 2]

What was wrong with the Old one?

The equipment fitted to the car along with the year would help also.

[tangerineshep]

What was wrong with the Old one?

The equipment fitted to the car along with the year would help also.

The old one kept throwing ABS codes (which I think are spurious) referring to the gear recognition signal being intermittent. Really struggling with it to be honest.

Here's the spec:

A8 2002 D2 2.8 Quattro
5 Speed Automatic w/sport steering wheel buttons etc.

I also thought that the combination of the recognition signal, coupled with a weird slightly noticeable cyclic rev thing when the car is running at 1200-1700 revs, could be as a result of a faulty TCM. I had read elsewhere that an ABS fault of this nature is usually down to the TCM; Ross-Tech also (helpfully) said to look for TCM codes of which there are none which is frustrating.

So far I have done the following:

Replaced a faulty solenoid in the valve body which also gave me the opportunity to do a gearbox flush. (that was as a result of a code flag)
Cleaned ABS sensors - and replaced a CV boot which I dont think was the issue
Had the wheels balanced again
Replaced the battery
Carried out a throttle body alignment
I've also changed the coding on the original TCM to see if that would have an impact.

To be honest, it's just niggling now. The car does run/change gear etc pretty well but this spurious code and the cyclic revs has really thrown me.

Thanks for getting back in any case