Customer has a 2016 Cadillac ATS-V with 8L90 transmission and 12,000 miles on the odometer. Engine, transmission and tune are all completely stock. The problem is exhibited in cruise control while traveling down a highway. The following behavior is clearly visible while creating a log file while in cruise: while on the (at least somewhat level) highway, set the cruise control to the speed limit. The exact speed doesn't matter much since the problem and replicated at speeds from 50 to 90 mph. Begin logging and monitor the TCC line pressure. One can watch the TCC line pressure slowly begin to 'leak' down. Once the pressure has decreased to some point (about 29 at 70 mph), the torque converter unlocks. This can also be seen as a rise in the engine speed of about 200 rpm or so. TCC pressure is quickly restored (as this only takes about a second) and the converter again locks, the engine speed decreases appropriately and the TCC begins slowly decreasing only to repeat this cycle. This entire process is repeated about every eight or nine seconds indefinitely.
Customer has spent hours at the dealer, took them for rides to demonstrate the behavior, logged a service incident, and involved the District Manager for "Aftersales" who eventually started dodging his calls. The local dealer has replaced the converter, re-flashed the car, changed to the latest-and-greatest fluids and now states that there is nothing else they can do. As an aside, the local dealer Service Manager also drives one. As soon as the customer demonstrated the behavior in his car, they immediately returned to the dealership and went for a ride in his car. It did the same thing. The Aftersales Manager 'talked to someone in Detroit' who has one, and confirmed the same behavior. Their conclusion was that since they ALL drive that way, they are performing as designed.
I spent a few weeks working on this from a tuning perspective, and was never able to eliminate the issue. Wondering if anyone else has run across this before and if so, were you able to resolve it with tuning?
I've attached the stock tune file and a scan clearly showing this issue.
Thanks in advance!