So let me preface this by saying, I am not looking to start a whole new A8 blast thread for the umpteenth time on the forum, so A8 haters can stop reading now.

My A8 has done something very curious twice now, and I am wondering if anyone else has seen the same thing...

It is a 2016 Z51, build date of October 2015. Transmission has been flawless operationally, and I am not easy on it at all. It has been perfect in every way.

But two different times now, I have had a condition wherein I start the car, the check engine light is on, and the transmission is stuck in 4th gear, no matter if it is in "D" or "M" mode, almost like it is in a "limp mode". Also, when putting it into gear, it hesitates, then clunks into 4th gear. Reverse still works normally as well.

The only way to fix it that I have found, is to disconnect the battery for a minute or so, and then reconnect. Everything is normal after that.

After some thought and correlation, it occurred to me that the only thing I have done out of the ordinary each time it has happened, is that I had turned the ignition on and off a few times, without starting the car (like to roll windows up or down). I plan on trying to re-create the condition, now that I figured that out to be sure, but was wondering if anyone else has experienced this particular issue (not any other issue, just this one)?

UPDATE:
So I just found some other info about this, and it seems it could be related to the use of the Range AFM disabler (which I have). It may be because I leave it plugged in all the time, and it doesn't like on/off ignition changes.

UPDATE 2:
It is the Range module. After extensive testing, I only have the issue under two conditions:

1) If I turn the ignition on and off a couple of times and then try to start the vehicle. If I know I am going to be turning on and off the ignition only, then I just pull it out beforehand. When I am ready to drive, I put it back in and it isn't an issue. No problems with it, as long as I remove it when turning the ignition on and off repeatedly (like to roll up windows, or listen to radio, etc).

2) Jump in car and start immediately (like a few seconds after opening door). It seems like the car needs a short amount of time to boot up, before starting the car, or it can get confused. This has only happened once so far, and it was a very short time between opening door and starting.

 

Tcm costs under 300 so if your not sure it could be nice insurance/piece of mind.

I had to replace mine.

 

Cool thanks. I am still under warranty, but I try to avoid dealer service visits at all costs. It seems it could either be my Range AFM causing the issue, or possibly a loose ground in the back of the car.

I think the ground issue is unlikely, as it only happens when the car is off, and then started, and others with this issue that had a ground fault were having it happen while they drive. It is easy to fix when it happens, so for now I will see if I can reproduce this weekend, and verify it is the Range AFM device.

Whatever the case, it would seem the TCM does not like power on/off cycles in a rapid manner, so I will need to be cognizant of that as well in the future.

 

Can you please point me to the source of this? I have the Ranger AFM also. I never had the problem you are describing, but I have had other weird small problems that I cannot track down that are very intermittent.

Thank being said, definitely try removing the Ranger before you bring it in and see if it keeps doing it.

GM replaced my complete tranny back in June 2015 with 100 miles on the car as the TCM was bad and it would cause all kinds of shifting problems, car would back fire, and loose connectivity to the TCM altogether. Back at that time, GM would not let the techs replace the TCM standalone.

Don't just buy a new TCM and expect to replace it yourself, unless you can flash it. I was told they come blank.

 

I saw it on this thread...
https://www.corvetteforum.com/forums...-4th-gear.html

 

I'm having exactly the same issue with the Range device. 2016 A8, Z51. Has Range responded with any feedback on this issue?

 

I am sure it's the Range and I have a feeling it's a special feature for 2016 (and maybe up). I can get my 16 Z to do the same thing by aborting a TCM flash before it starts, then fix it by reflashing, which was not a problem with 14 or 15. I bet that Range powering up is interrupting something with the TCM boot process on the 16 (which do have some differences ECM/TCM wise from the earlier C7s).

 

It is the Range and mine did it while on a trip earlier this summer. It will happen at startup when a lot of communications are going on over the network and the Range module creates a communications error with the TCM. Range is supposed to have an update and I will send mine in this winter, in the meantime I mostly just use the paddle shift. You can also plug the Range module in after startup and this shouldn't happen. Range has had similar issues in the past and provided updates to correct.

 

FWIW: I just received this information from Range about the problem > https://rangetechnology.zendesk.com/...-Engine-Lights

 

It is the Range module. After extensive testing, I only have the issue if I turn the ignition on and off a couple of times and then try to start the vehicle. If I know I am going to be turning on and off the ignition only, then I just pull it out beforehand. When I am ready to drive, I put it back in and it isn't an issue.

No problems with it, as long as I remove it when turning the ignition on and off repeatedly (like to roll up windows, or listen to radio, etc).

 

My Range module only caused the issue when I used the remote start (not every time but randomly and infrequently).

 

Haven't had any issues with that at all, use it all the time, but good to know if it does happen!

 

I had been using the Range module since the first of April and it didn't do it the first time until I was on vacation in TN in late June. I remote started it at the hotel and found I had 4th gear only. It repeated once in late July so it is infrequent but still annoying when it throws the code.

 

FWIW: Range replacing my device. If you are interested they'll just swap it out for you.

 

Thanks! I will contact them today. I had been planning on waiting until my Z06 goes into winter hibernation but since they have a fast turnaround I will go ahead and get mine replaced or updated as they see fit.