75ZT Community

Had a very good and successful afternoon with the T4 (Testbook version 4.Computer Diagnostic System) today .

Over the last couple of weekends I've been involved with the retrofitting of electric back windows to a ZT V8, the mechanical and wiring part of the upgrade had been straightforward but the stumbling block to getting them to work was down to the ZCS coding and the fact that new highline BCU (Body Control Unit)'s of the correct part number are no longer available.

Firstly a replacement BCU was fitted and configured on T4 but of course because the coding wasn't present the windows wouldn't work.
I recalculated the codes and obtained the checksums the next problem was getting a V8 to a state where it would request new ZCS codes (using the normal method for the other models doesn't work)

Thanks to some information obtained this week that confirmed what I suspected, we tried again today and sucessfully inputted the new codes and the windows now work as they should. (as does everything else)

Result.

Many thanks to Mick for letting me loose on his very nice supercharged V8 460 and having faith in me for what we were attempting to do.
Also a great deal of thanks to David and others who have helped in no small way to make it all possible.

Together we've learned a lot, done things previously thought impossible or only known to a few all of which will be used to help owners in the future.

All in all a great day.

Russ

Nice work there sir you have been awarded some pies

Well Done Russ.

What you and that T4 can accomplish clearly knows no bounds.

Chris

Interesting, and good news.

I had been thinking about easier methods of getting the rest of the cars to do it, after a discussion with David yesterday.

My theory was that any of the units with the ZCS being swapped would have the same effect. Does that tie up?

Duncan

Well done I suppose the same principle could retro fit CC on my CDti to have full function instead of partial function at present although I believe its a tricky operation.

Well done Russ, great news!

I think the only trouble xpart have identified is that things like "one shot up" go awol for no reason. It's good to know that between members the combined knowledge knows no bounds and almost anything seems possible!

It would be better if you could do it by just using a menu on T4, I'm sure that T4 is perfectly capable of doing it, it's just that the programming doesn't have those menu options included.

You can only force the entry of new codes by confusing T4 by using "foriegn" components which hold the central coding key (only 4 of them do).

I've been thinking about the loss of funtion especially one shot up (which personally i don't use anyway) as it's an option on the dealer config menu, if it was known to cause a problem would it not be easier to disable it first, calculate the codes, rewrite the codes for what you are attempting to do, then re-enable it, or is that too obvious?

That would'nt help with Rob's problem though.

I'm sure that with enough "experimentation" we might be able to do almost anything.

Russ

If the one shot is a dealer option, we should be able to work out which bit controls it. Read the code. change it, read again. The bit that changed tells you which bit controls it. Of course turning it on and off after entering the new xpart one would work, but we shouldn't need to make the error in the first place.

Is it not already in the table myself and David worked on? If not then we should be able to add it.

The problem with things like Robs problem is as you can't switch it on or off, you can't see which bit changes.

I can narrow it down to just a few: I know which ones changed on my 04 plater when I used a T1 on it.

If I get some time over the next couple of weeks (I have some holiday at last) I'll see what we can figure out.

I'll have a look at the work we did before and see if it's clear.

I've been giving it some more thought and what may be happening is that the software in the later versions of the BCU use the codes in a different way so that when the coding for the BBS and powerwash are applied it affects the BCU in a different way to that of the earlier model BCU's that would account for the loss of function perhaps?

Russ

Not sure.

I think David said to code the BBUS in and out you have to use an older disc. So if that's the case, the older disc would assume the bits that started to be used for later features like the boot release from a long press, were not used and automatically set them as zero, rather than rewriting them as they were before. That's certainly what happened to my facelift tourer when I coded it to have satnav.

I think the xpart calculations may have another explanation. They may have never been given some of the bits, so their calculator again assumes they should be zero, or just has a mistake in it. If it's an excel spreadsheet someone could even have corrupted a cell meaning it never calculates correctly.

If things were done sensibly, you would not have the same bit doing different things in different BCUs. Doesn't mean it didn't happen, but even if it did, I'd expect the T4 to look at the BCU software and work out which version, and I'd expect xpart to ask which version you had before calculating the code.

But then again, you could be right. When we really have enough confidence that we can put back original values, we could play a bit, and check individual bits.

I've already identified the part of the code which controls the oneshot up. I don't understand why it would be affected to be honest. Russ your idea maybe plausible, just needs trying, maybe it just comes down to identification error at the dealers. They fill in a form with the car spec so it could be easily missed. Just odd its the same thing that goes awol. Anything post 2004 would be affected by using a T1 disc I suppose. On some upgrades it may just work out easier to write the ZCS codes instead of using the Testbook CD's. I'm going to get some OBD (On Board Diagnostics) sockets and plugs and attempt my idea, it may work, it may not.

On robs car I think digit 12 of the SA string is currently '9' and needs to be 'D' I did sit and work it out but then never wrote it down

I think there's quite a few good valid points there. I can see the obvious one being an incorrectly filled in data sheet at the dealer.
Far better the way we do it by looking at the original coding then using the calculator to see what's fitted.

Chances are the earlier disc doesn't know the coding for remote boot release so it won't enable it.

I think you're right for some upgrades and retrofits it may be far easier to calculate and apply the new coding rather than using the early disc depending on the age of the car to be upgraded.

I'm getting to grips a bit with BCU's and the only differences in them I can see are the pre-installed base software versions, surely if all BCU's worked the same way then they'd all have the same part number?

I wonder if you fit an early type BCU and enable it to a facelift would it work the remote boot release?

Will have to have a go at that one if I get the chance, that would certainly prove if the base software has any influence on what it will operate. I guess it's something we'll need to find out for the future.

Russ

I don't think all BCUs would have the same features. Some features were only thought of later, like the boot release. On launch cars that was for memory seats and there was a keyswitch in the bootlid.

Later on they wanted to remove the keyswitch so change the function, so I'm guessing the software was extended at that point. But the sensible thing would be to extend the software so it would be backwards compatible. That is the latest software would work just the same as the oldest, if coded right. Previously unused coding bits would be used to control the new features, with the old ones doing the same as they always did.

I would expect an older BCU to ignore, or maybe even reject a coding wityh the bits for the new features set.

I think this is effectively what the older testbook discs do. When you change a feature, they read the existing coding, modify the bit or bits that control the feature you are changing, and write it back. However if they don't know about a later feature, they will just write a zero in that bit position, ignoring whatever was there before. This is exactly what happened on my facelift where the first time I wrote a new code using the old T1 disc I had, it turned off three bits that were nothing to do with the feature I was turning on. From memory, two of those were 2004MY and EOBD bits.

We are probably all saying the same thing actually, so probably worth having a face to face at some meet sometime.

Well more fun and games.

Just had a ZT over for a session and to enable a new key and alter some dealer options.

I notice that although anti-trap was fitted one shot up was switched off. When I tried to enable it the menu button changed to a question mark continuing from as normal produced a screen saying it was a configuration not possible for this vehicle.

So the plot thickens, so it may not be possible to enable one shot up if the coding for it is not already present.


Russ

Interesting. I wonder if some other feature is mutually exclusive. For example if the car was coded as USA (is this an option?) it might refuse to allow one shot up?

I don't think this will be the actual setting, it's just an example off the top of my head.

Another possibility: did some lowline (two window) BCUs not support the antitrap, therefore not support oneshot?

This was on a highline BCU (4 electric windows) so I was surprised to find that it wouldn't enable the one shot up especially since the car was fitted with anti trap.

Although on this occasion I didn't get a copy of the coding due to weather and time constaints when I catch up with the car again I'll note them down and try to figure out what's going on if possible.

I think I'll start to note down all coding and which dealer options are enabled from now on, so that I have a database of different codes especially those with different combinations of options fitted.
That way we could look at the coding for example of a 1999 car of the same spec as a 2004 model and see if there's any differences



Russ

Yes, that's a good idea. Between myself and David we already had a few, and that's how some of them were figured out, plus which bits the older disc switched off, on my 2004 car.