Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2015 Infiniti Q50 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2015 Infiniti Q50. The contact stated that while driving at highway speeds, the vehicle inadvertently slowed down. The vehicle failed to accelerate. The check engine warning light was illuminated. The vehicle was towed to the local dealer where it was diagnosed that a valve body replacement was needed. The vehicle was not repaired. The manufacturer was contacted, and the contact was informed that the vehicle was not covered under warranty. The failure mileage was approximately 56,000.
When on the highway my transmission slipped then went out and wouldn't accelerate, without any warning or sign of trouble beforehand. I scrambled to pull over and it started to accelerate again. It struggled to shift in 1st gear and second but despite going over 40 mph it would not shift to third gear. I could feel it slipping/sputtering when letting up on the accelerator and jerk when I press on the brakes. The engine will continue to rev high at lower speed. My check engine light came on and gave two codes, P0720 and P0500. I took this to my mechanic and he advised the valve body that houses the AT speed sensor be replaced and I likely need a new transmission. …
4/16/2023 Sunday 5pm With my wife and daughter in the car, I started the vehicle in my driveway and selected Sport mode as usual. Selected reverse and backed into our turnaround then forward to the end of our driveway. Driveway is approximately 4 car lengths long with a 20 ft long apron turnaround. Almost immediately after braking at the end of the driveway while waiting for passing traffic to exit drive, vehicle suddenly accelerated and I immediately pressed the brake as hard as I could to prevent driving into passing vehicles. I could hear the tires trying to grip/spin while I was fighting to press the brake harder to hold it t back. I then panicked and selected the gear shifter to anything other than drive and it immediately did the same in reverse. After getting in into park, I immediately selected Standard mode and the vehicle performed normal afterwards. …
While driving on the interstate and coming over an overpass there was unavoidable debris located in the road. Immediately after passing over the debris there was a loud noise followed by jerking and the RPM's revved up almost like the car was in neutral. I let up off of the accelerator and then tried to accelerate again. The car would not go faster than 30mph and will not shift out of 3rd gear. I had the car towed to the dealership and the diagnostic codes reflected vehicle speed sensor and there was no physical damage that was visible under the car. I was told that the problem was in the transmission and that it would need to be changed and given an estimate that totaled over $10,000. I was also told by the service advisor that this is a known issue with the Infiniti Q50. …
While driving my 2015 Infiniti Q50s, the transmission suddenly suffered a catastrophic electronic failure, causing the vehicle to immediately drop into "limp mode." This resulted in a sudden and dangerous loss of acceleration while operating in traffic. A diagnostic scan revealed trouble codes P0500 and P0720 (Output Speed Sensor circuit). However, following Infiniti's official Technical Service Bulletin (TSB ITB19-040), the actual failure was the Transmission Control Module (TCM), which is permanently integrated into the transmission control valve body inside the transmission. Because the speed sensor cannot be replaced independently of the integrated module, I was forced to pay out-of-pocket to replace the entire transmission control valve body assembly and have a dealership program the new unit. …
Transmission, Transmission Valve body, speed sensors. After transmission shifting issues while traveling the interstate I had to have the car towed to the dealership. After the multi point inspection was performed serveral recommended itmes related to the ongoing performance and SAFETY of the vehicle listed below: Transmission $10,446.65 Transmission Valve Body $3693.92 The diagnostic code P0720. Attached is the service bulleting stating they know this will happen and when it does here's how to fix it. Yet they have never recalled the defective transmission. When I contact Infiniti consumer affairs they simply say that they cannot help me because the vehicle does not have warranty. If i had warranty then I would not be reaching out to them for assistance in replacing the transmission.
My car would not accelerate over 40 mph randomly after work. Once i noticed and tried to shift to a lower gear the car did not shift gears at all. When these things first happened there was no indicator lights on. The next morning the check engine light came on and the code pulled was P0720. After finding a repair shop to look further into the issue I was advised the car needed a new transmission to fix the issue. $4,000+ for the repair and as i google the issue I see that this is a common issue and it seems to always happen unexpectedly side note: also should be a recall on driver side blend door.. i almost died this summer due to cold air only blowing on one side in the middle of summer in 100 degree weather.
The car was being driven on a normal day and while in gear and driven the car stalled and would no longer shift automatic. The car will not come out of 3rd gear. Took the car to repair shop and was told is a known issue with this model and even the transmission or transmission valve body needs replacement. Infinite will not issue recall and I have reach out to corporate on the issue the repair want 8,000 to replace transmission the car is out of extended warranty that was purchase on the vehicle I'm only the second owner of the car well maintained and should not be having this issue of a self maintained transmission with a vehicle worth 25,000 wen brought.
My Car Suddenly Stopped In The Middle Of The Road With A Check Engine Light. I Have a P0720 & P0500 Codes Indicating A Vehicle Speed Sensor & Output Speed Sensor Failed While Operating . This Cause My Transmission To Fail And Not Shifting. I Am On My Way To The Dealer Now . Hopefully Infiniti Will Do The Right Thing And Fix It . At 56,000 Miles A Transmission Should Not Fail . Unexpectedly Almost Causing A Car Collision . No Prior Warning Was Provided By The Car . The Car Just Suddenly Failed . This Is A Very Serious Safety Concern .
The speed sensor on car seems to have failed unexpectedly while driving over a bridge. The car would barely move and could have become a dangerous situation for multiple people had it been typical traffic. The issue seems to be that although the sensors are corrupted, the entire valve body or transmission must be replaced to solve the issue leaving the car inoperable. The car is currently at a repair shop. The engine light did come on shortly after. PLEASE ISSUE RECALL. https://static.nhtsa.gov/odi/tsbs/2019/MC-10168892-0001.pdf
Acceleration complaints in other Q50 years
Frequently asked questions
How common are acceleration problems on the 2015 Infiniti Q50?
NHTSA has 21 complaints about the speed control & acceleration of the 2015 Infiniti Q50, 17% of the model year's 126 complaints.
Is there a recall for 2015 Infiniti Q50 acceleration problems?
No. NHTSA lists no speed control & acceleration recall for the 2015 Infiniti Q50, though it has 3 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2015 Infiniti Q50 acceleration problems start?
Half of the complaints with a recorded mileage happened before about 56,000 miles, and 40% before 25,000 miles.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.