Automatic Transmission Control Module problems of the 2015 Infiniti Q50

Transmission valve body failed while driving which caused shifts to be limited. It could have caused an inability to shift at all, which is a safety issue. This issue has been inspected and confirmed by an independent shop. No warning signs were present before the failure. Furthermore, this issue is well known to Infiniti. It’s caused by breakdown of the transmission fluid overtime, causing a reduction in the cooling capacity of the fluid. But Infiniti says that the fluid should be lifetime. This overheating causes the tcm on the valve body to fail. If it failed while I was going at a highway speed I could have been injured.

Just over 1 week ago, I was leaving a parking lot and driving back to my home when my car wouldn't accelerate past about ~10-15 miles per hour and wasn't shifting gears. When I took my foot off the gas pedal, the gear just dropped immediately from above third to first gear and the car shook. I first noticed this when already out of the parking lot and pulling off from a median onto the road, with no engine light or other warnings. I quickly pulled into the turn lane where there wasn't traffic and turned the car off and back on. It was the same but luckily I was in eyes view of my apartment, so I drove under 10 mph and made it home. I took the vehicle to a transmission service center and the error code that came up on the computer was (p0500 - vehicle speed sensor a), which the service center said is an issue with the "valve body" inside the transmission, specifically the "tcm - transmission control module" that sits on top of the valve body. I contacted multiple Infiniti service centers and they all confirmed that the valve body for my vehicle (part# 31705-x133a) is back ordered by over a month and could be longer until they have it. They do not sell the transmission control module separately. The valve body was quoted to me for $2200 for the part alone. I attempted to install an aftermarket valve body and a new error code came up on the computer (po720 - output speed sensor circuit). I kept the original valve body and will hold onto it. Doing some more research, this appears to be a common issue with the Infiniti Q50 - [xxx] in addition to the reddit thread above, a quick google search for Infiniti error codes p0500 and po720 point to multiple sources indicating the same common experience and outcome. My vehicle has 110k miles and users in the reddit comments are also reporting the same issue with the tcm transmission control module occurring between 85k - 100k miles in all cases. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

The valve body/tcm shorts out on the car unexpectedly and can happen at any time causing the car to be unable to go past third gear. This is an known problem with 2014-17 Infiniti Q50 & there is a service bulletin issued by Infiniti associated with this problem published in November 2019. This vehicle was inspected by Infiniti dealership and they confirmed the issue. There was no warning light or prior to this event. After the failure this codes popped up p0720. Repair was ~$3500.

The valve body/tcm. Yes the vehicle is available for inspection. The valve body/tcm shorts out on the car unexpectedly and can happen at any time causing the car to be unable to go pass third gear. This can occur on the freeway, or when trying to avoid an accident. This is an known problem with Infiniti’s & there is also an service bulletin associated with this problem. This vehicle has be inspected by the dealership and they confirmed the issue. There are no warning light or and thing prior to this event. After the failure this codes popped up p0720 & p0500. This occurred on Aug 13, 2022.