Denali05

I had hoped that Acura has figured out most of the issues with the ZF 9 speed, but it seems that I'm in the unfortunate small group that continues to be see issues with 2018 TLX models year. I've been experiencing some intermittent rough shifts between 1st through 4th gears. During upshifts under light to moderate acceleration, there is a noticeable forward jerk. In some 1-2 upshifts, the engine will surge approximately 1K RPM while it is shifting along with a feeling of loss of power and engine braking during the upshift.

After two visits to the dealership, the technician performed a throttle position clear, a crank pattern relearn, an idle relearn, transmission teach in, and lastly a static and dynamic learn procedure. All the aforementioned work seems to be standard for a transmission relearn. What stood out to me was that he also found code P2638, which as far as I can tell, is related to rough shifts for 15-16 TLX models. The technician cleared the code and did not find any software updates available.

I received the vehicle back today and after driving around a little bit, the shifts do appear to be smoother, but I'll have to test it a little more to be sure. I'm wondering if anyone else has had experienced this code before, either in 2018 model year or 2015-17 years, and what you had to do to resolve this?

Transmission Function Improvements: Sensation of Surge While Braking, Slow Downshift Response at Low Engine Speeds, DTC P2638 and Other Listed Symptoms

Mr. ShawnJ007

Just out of curiosity, what brand and grade of fuel did you put in last? before that? Fresh tank or top-up?

Denali05

Last fill up was 91 octane grade from Costco's gas station. 90% of my fill ups are from that station.