Hello Everyone,
I have a 2015 Z51 with 8700 Miles and am having some electronics issues that are getting worse and worse. It started with the car giving the service rear axel light a few times. So we took it to the dealer where they said there were no codes and nothing wrong. They checked the records and the battery in the car was replaced two years ago and that it should still be good. They said it was likely because the car had been sitting for a while and that by driving it more it should stop. After daily driving it for a week where the light came on one or two more times, I put a range device on the car. (I had been driving it in manual mode to protect the A8 until the range came in). During the next week of driving it I had noticed a few times when getting into the car that the clock had been reset and the car had been returned to touring mode, which was strange because I only drive it in sport. This probably occurred 2-3 times. Roughly 5 days later when driving on the highway I gave it some gas to accelerate and get around someone, roughly from 1/3 throttle up to 2/3 throttle, and all of the electronics in the car shut off for 2-3 seconds. I do not believe that the engine shut off at this time, but the car lurched when the electronics shut off. Something else to note is that the cruise control stopped working, the indicator showing that it was enabled but not set was on the dash, but you could not set it or turn cruise control off all together and make the indicator go away. I immediately started heading home as I did not know if the car was going to completely die and strand me. On the way back I had to cross some railroad tracks and when slowing down I felt the power steering get heavy and a service stabilitrac warning came up on the dash. 15 minutes down the road I began decelerating for a turn and the car bucked again and the entire dash and infotainment screen went blank once again, I believe I also felt the power steering get weak again. about 3 miles later it did it again. I got it home and called the independent shop a couple of miles from my place and told him that some of the things I had seen on the forum in regards to the service rear axel light said that it was likely the alternator. After leaving the car with the mechanic and he checked the alternator up and down and even read the battery voltage from where the line went into the alternator he said that everything read strong. When he came to drop the car off and me take him back to the shop in my truck the car apparently failed to start 3 times but fired up with no hesitation on the 4th attempt. When arriving at my place a warning came on the dash that said service anti-theft system. This was also the first time for that warning. After speaking with my father, he thinks that it's coincidental that this started after installing the range device, I disagree, but am going to take it off and drive it to see what happens. If anyone has an idea as to what is going on please let me know. I am thinking I may end up replacing the battery anyways. But the car will likely be going to the dealer to have an extensive check up once the mechanic who takes care of all of the family performance cars is free, but he currently is swamped and said he wouldn't be able to get to it for a week or two. Many people bring their cars, even non GM cars to this dealership specifically for his services as he is the best anywhere outside of the major cities.
Sorry for the long post but thank you for any help!

 

Too long to read! I got hit by a wall of text.

Listen up! When electronics start going ape $hit, the first question that we ask is, "How old is your battery"? Let's start there, How old is your battery!

Elmer

 

Battery is 2 years old

 

Did you ever run it down and have to jump it?

 

No not once, so far.

 

Set the dash display to Tour / Performance where you can monitor digital battery charging voltage. If you see spikes to 15 volts when the problem occurs the alternator / voltage regulator is suspect.

Otherwise, flaky batteries seem to cause all kinds of issues. Batteries can fail at any age.

Let us know the resolution.

Ron

 

Yeah I drove with the voltage meter on after the first shut down and it stayed consistently in the 13 range

 

Your symptoms: service rear axle warnings, can't activate cruise control, power steering difficulty, IP gauges, and dash lights turning off all point to an electrical problem where insufficient voltage is getting to those features. The StabiliTrak warning probably occurred due to the power steering control module not sending proper steering angle information to the EBCM. The cruise control issue probably occurred because the voltage supplied to the ECM got a little low. A lot of times a fault in one subsystem that provides data to another subsystem will cause the dependent subsystem to shut down and display a service message. If the battery or some other circuit is drawing too much current and that in conjunction with other electrical loads exceeds the alternator's ability to provide the proper voltage to various subsystems those subsystems will shut themselves down or limit function based on the available current.

Assuming your two year battery is good based on what the mechanics have told you and some of your issues have occurred during a vibration event (railroad tracks) I would look for loose/corroded connections in the ground circuit and at the battery cables including the hot lead to the starter.

The voltage reading on the IP will vary depending on the number of electrical loads and the battery state of charge. The car uses remote sensing (of the voltage being applied directly to the battery) to make sure the alternator delivers sufficient current to keep the battery at the proper charging voltage. As the electrical loads change and the battery charge varies with time the dash voltage can vary between 12 and 15 volts. The voltage on my car typically varies from about 12.5 V to 14.5 V while I am driving.

The small gauge black wire that is attached to the battery ground cable is part of the remote sensing circuit. Make sure that the wire isn't broken (although if it is you should see a warning on the DIC). When I took delivery of my 2015Z I had a 167 mile drive home and the charging warning came up several times during the drive. The next day I took it to my local dealer and they found that the wire was broken. The wire is extremely tight with little slack and it is sometimes stressed when people disconnect and reconnect the ground cable. Sometimes the stress results in a subsequent breakage. If the wire is broken it can result in a battery that isn't charged properly.

Bill

 

You might have a ground that's not making a good connection. Might be a good idea to subscribe to ALLData for the service manual and trace all the grounds.

 

I have seen that issue here on the forum as well, after work today I am going to check that to make sure.

 

There has been an interesting development and the first like this that i have seen. But when humoring my father's theory, I unplugged the range device and drove it 25 ish miles, no issues whatsoever. I drove it here to the office today and am going to take it on my after work routine and see if anything else happens. If not I will do the same tomorrow and see what happens and if all is good I am going to contact Range for a replacement.

 

I hope it is that simple!

GL

Ron

 

I've always been of the mind set that any time you plug an accessory into the OBD port your asking for trouble. This port is the BUSS line that goes to every module in the car.
After many years of experience in the electronics field I've learned it does not take much to put noise on this line and cause issues.
The only thing I ever plug into an OBD port is a high quality scanner and I don't let it run for extended periods of time.
I'd remove the Range, run a scan on the car, clear any codes and run the car without the Range and see if that resolves the issues.
Needless to say I don't run a Range on my 17 but tuned out the AFM, nothing left on the port.

 

I too admit that I only read the first line; when I saw the age of the car I'd simply suggest a new battery for a start (and, likely an end). WAAAAY the most common issue in such situations. And, don't forget to clean and decrud the cable connectors. All the best!