Here’s the backstory,
For the past 3 months, upon shifting from 2nd to 3rd gear, the car lurches forward in a hard shift. Sometimes, it is nothing more than a benign “clunk”, and other times it is violent, as if hitting a wall. This does not happen every time it shifts and even under identical acceleration, the results vary from none to violent. The number of violent shifts vs. small jolts has increased over time, and all other transmission functions and shifts are fine/normal. After much time researching the inter-blogs, I have come to no consensus on what is causing this or how to fix it. Some say it is the adaptive shifting program and it just needs updating and others say it’s the tranny and a rebuilt tranny replacement is the only thing that eventually fixed this problem (though one posting on the Hyundai forum is of the same exact problem, but the solution is worrisome – contact negative battery terminal to positive, let sit for 10 min, reconnect, then drive at 1/3 throttle, shifting through all gears a dozen times. Poster says this resets adaptive shifting program and worked for him).
Finally, today, I took it in for a diagnostic with a local transmission specialist, and they could only replicate the hard shift once, but when that happened, he said the car went into limp mode and read two codes: P1193 and P2127. The car has never gone into limp mode (P1193) nor shown an signs of suppressed RPMs associated with this mode. Also, he seemed to focus his attention on the low voltage to the pedal position sensor (P2127) as being the major issue that is causing the hard shift. I also called a past dealer that worked on a similar issue with the car when I bought it used 4 years ago and they recommended updating the adaptive shifting program as they did last time; though I don’t recall if the shifting issue was the exact same problem I am having now. So, a few things I need help with:
- Does this sound like a computer issue or a tranny issue?
- Could the pedal position sensor having low voltage cause a shifting problem like this?
- Any merit to the connecting the battery terminals idea?
- Should I be wary of the mechanic that did the diagnostic today?