Thanks to the excellent Dave and co at Bristol Transmissions I'm absolutely delighted to report that the odd transmission fault that has plagued my RRS ever since I have owned it (4 years!) is finally fixed.

I've posted about this before so if so inclined you can read previous posts or look in my gallery for a detailed description but basically the facts are these:

There was a brief thump from the transmission after about 20 minutes from a cold start and it would repeat thereafter about every 20 miles.

If cruise was engaged it would be cancelled and sometimes the 'HDC fault system not available' warning would flash up on the dash. The fault code 'U0101-87 lost communication with TCM' would be recorded for the Transfer Case Control Module (TCCM). There was also an apparently unrelated fault code of B1B70 'local interconnection network bus circuit 2' from the Body Control Module (BCM).

Using the IID Tool to monitor live values revealed it was caused by the torque converter unlocking and re-locking within a second or so.

Further monitoring of live values ruled out various reasons for this including the wheel speed sensors and the EGR valves.

The first thump always seemed to coincide with the engine and/or gearbox reaching full operating temperature. Further live monitoring and recording of all available temperatures and related voltages showed that there was something odd about the gearbox temperature sensor voltages especially the supply voltage which spiked to zero coinciding with the thump.

Unfortunately the gearbox temperature sensor (which is the thermistor type) is built in to the transmission control module (TCM) which is an integral part of the gearbox mechatronic which is situated inside the gearbox sump. So changing it is not a small matter.

Finally after trying many simpler fixes the job was handed over the the experts. The gearbox sump was dropped and the mechatronic replaced with a good used unit fitted with a new set of valve bodies.

The problem is now resolved. None of the fault codes and messages mentioned above now re-appear. Hallelujahj!!

Big thanks to Bristol Transmissions who did the job at a very fair price.  2008 MY Java Black TDV8 HSE

Must be like driving a new car.  

Supporting the London Air Ambulance with my Brothers

Congrats!!!! Isn't it nice to know you can now get into your car without fear of some fault popping up...