I have a new issue on my 73k mile XJR:
At the end of some recent "spirited driving" (much harder than my usual),
I got the light and "transmission Fault" message and the trans went into the default lower (4th?) gear.
Started out ok with the next start, but the light comes on again and it defaults almost immediately now. (I think it took maybe 15 minutes at first?)
An independent shop near where this happened pulled codes PO701, 729, 730, and 735, and thinks the "trans is toast", but:
I see that the 729,730, and 735 codes all reference a possible "ECM torque signal fault" (or dead trans), while the PO701 shows a possible "TCM/control valve failure or DSC fault".)
I think I did get a message about DSC not operating, too…
Does this scenario ring any bells?
This is a first-ever issue for the car, which I love… a new trans. would be a big hit, though.
I had to drive the car maybe 100 miles to get home. It's now in Monterey, Ca., where I have no experience with the dealer… (any experience with them?)

 

A simple re-load of the TCM software may, (probably will), cure the problem. At your mileage, it's probably time for a fluid flush and filter change if not already done. As the box slowly wears imperceptibly, the fluid pressures can get such as to trigger a fault. The TCM system has a watch-dog that monitors things like fluid pressures at changes, and if anything looks at all dodgy, flags a fault and puts the transmission into 'Limp Home' mode.

I had something similar to yours in 2011, and a software reload cured it.

 

Fraser, thanks.
I'm a little at sea here, though… the first three codes reference an ECM fault (or dead transmission), and only the 701 code refers to a possible TCM fault…
I understand that I'm over the 60k mile (now) recommended fluid change and am ready to do that (if the trans is good).
But if the electronics aren't sorted by reflashing the trans software I need to save the money for a rebuild...
Or would a reflash sort an ECM problem as well as TCM problems??

 

The TCM, (located in the gearbox) communicates with the ECM via the CANbus via a plug and socket at the gearbox. This has a seal that on early cars starts to leak and the individual contacts on the plug&socket can get dirty and corroded thus causing problems. So as well as a fluid change, it is standard practice to replace this seal and clean the plug and socket. The seals were improved at some unknown date, but definitely after 2004.

So my opinion is that you don't need a new transmission. Of course I can't guarantee a fluid flush and new seal and a TCM reflash will work for you, but it worked for me.

 

Similar story with my SV8.

Prologue:

I felt harsh shifting 1-2 less 2-3 and back as well as well-known lurching when car is cold and clunk kick in the back when car starts to roll from standing and you lift up the gas. These are all well-known bugs and reported many times in internet. Also I experienced quack noise from tranny when going WOT and shifting 2-3. I even found official service bulletin with description to add additive into trans oil related to that quacking. I started with simple - decided to clear adaptations. Went to a dealer. They spent 3 hours! in total and reported cleared! Let the car to learn for some time. I let.. I was slow like grandma at first day on the road.. Frankly, nothing improved. After some spirited driving all the symptoms were back. Today I feel they did nothing that time.. not a surprise - clever dealer is like a snow in the summer nowadays especially on “gold car customer” sector, I hope you understand what I mean. So I decided to go further – to change oil and filter. Quack gone. Lurching gone for a while and shifting became smoother but not much improved. I read internet more and almost decided to renew solenoids which is very popular at bimmer owners as they have the same 6hp26. That is not cheap but cheaper than used transmission without history. Time was going and I kept driving with that ****. My feelings to the car became colder and colder.. I got gearbox fault around once a week after heavy kick at 1-2 shifting with 2nd gear holding till the cutoff at red line that happened in slow daily traffic conditions no racing or drifting. I spent almost half a year with that car’s behavior and almost pushed the trigger for used transmission.. but decided finally to reflash the tranny by myself and clean my conscience that i did all my best to fix it without surgery, however that stupid dealer where I cleared adaptations told me that firmware on these cars is not upgradable and factory stopped any developments on this generation. Bought chinese Mongoose Pro, downloaded 139 SDD with upgrades up to 139.8. Installed on Win7 on Virtualbox after that all upgrades were rolled on via internet smoothly till V139.17 (spent two days in total for all SW preparations) and went for a try of connection. Connected without issues three clarification questions on car options installed after auto VIN scan and you are ready to diagnose. Any solution in SDD starts from full diagnostic of the car. I got one fault related to ECM with something like engine load on gear and one related to TCM with something like gear ratio fault. I read that I need voltage maintainer for any reflashing tasks as its very risky to turn the car to big stone on wheels if voltage drops. Ok I said. Let’s just clear the adaptations as I thought that process is like clear DTCs - easy and quick - and after trials I will come to my friend’s garage with voltage supplier and do complete firmware update. But when I chose that option I was confused by SDD that it was required reflashing of module to clear adaptations. I was really confused but decided there was some miswording and I can try. I pushed the trigger. Oh Mama.. car closed the doors switched on DRLs and began reading or scanning.. 5mins.. 15mins.. 30mins.. I abused myself what a stupid step I did that car will die now without power supply.. live and learn I thought.. but after 36-38mins stopwatch stopped and flashing completed.. Do you want to load calibration file? SDD asked.. yes or no.. surprise number two as I only wanted to clear adaptations if you remember. I pushed.. yes.. stopwatch started again.. 5mins.. 15mins.. 30 mins.. damn, what a stupid step again haha) finally after about the same 36-38mins downloading completed and nor battery in the car neither my laptop died as it was just on the street.

The point:

Car now feels like Rolls-Royce.. shifting can’t be felt at all!!! Even when you move selector from parking to drive or reverse nothing pushes the car when you hold it by brakes! It’s a MAGIC!!! I fell in love again I spent whole day driving at some not mandatory destinations.. just driving and feeling this cat’s grace and smooth. Throttle now feels connected to engine and car literally follows your leg like on mechanic! Will see how long will it last.. but I could not believe it can be fixed like that. But anyway now I still have a question. What I really did by that “adaptations clear” procedure? Should I renew the firmware anyway by separate procedure for that or that was already done by flashing and downloading calibration file? Thanks everybody and never give up with these magic cars )

 

If it is working fine, leave it alone. These ZF six speed transmissions can operate as well as any. Fluid and filter change will keep it operating that way for a long time.

 

58 minutes to clear the adaptations!


I'll report back with results.


Next I have to figure out how to fix the shocks. They are all at max height and stiff!