2015 Infiniti Q50: stuck in gear or won't shift

Filed Aug 12, 2026 · Transmission · VA

While operating the vehicle, the transmission suffered an abrupt failure resulting in Diagnostic Trouble Code (DTC) P0720 (Output Speed Sensor Circuit). Further diagnostic inspection revealed a complete internal failure of the integrated valve body assembly, which houses the Transmission Control Module (TCM), solenoids, and output speed sensors. The failure caused an immediate loss of gear selection, restricting the transmission to 3rd gear ("limp mode"). Attempting to accelerate beyond 3rd gear causes violent vehicle shaking, severe hesitation, and an inability to maintain traffic speeds due to the TCM losing signal input from the speed sensors and solenoid circuits. This total valve body/TCM failure creates a critical safety hazard. Sudden restriction to 3rd gear without warning on highways or during turn movements leaves the vehicle unable to match surrounding traffic speeds, creating an immediate risk of a rear-end or side-impact collision. The vehicle has been strictly maintained according to manufacturer schedules. Because Nissan/Infiniti designed the TCM and speed sensors as an integrated unit inside the hydraulic valve body, a sensor failure requires replacing the entire valve body/TCM unit—a repair quoted at over $3,000, with complete transmission replacement exceeding that cost. This valve body/TCM failure mode is widely documented among Infiniti Q50 owners sharing the RE7R01A 7-speed automatic transmission platform, indicating a widespread electronic and mechanical defect that threatens driver safety.

Filed Jul 15, 2026 · Acceleration, Transmission · AL

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. This is a widely documented, premature failure on this vehicle platform that creates an immediate highway safety hazard when the vehicle drops power without warning.

Filed May 27, 2025 · Transmission · TX

Transmission intermittently will not shift to the next gear. Sometimes will not shift from first gear, other times will not shift from 3rd gear. Sometimes no issue at all. It is intermittent and no warning to when the issue might happened. It happens when trying to accelerate and has put me in an unsafe situation trying to accelerate on the highway or around town.

Filed Mar 19, 2025 · Acceleration, Transmission · LA

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. After doing researching this a common problem and the consumer is having to pay out of pocket if the warranty has ended. This incident could have ended badly while doing 70mph on the interstate and the car just quits moving. With all of the complaints that I have read over in regards to the transmission issues yet no action has been taken to investigate this problem. It is obliviously a manufacturing issue and the consumer should not have to pay out of pocket for defective transmissions. This luxury car was not a cheap purchase. Very disappointed that with so many cases an investigation has never been done. Infiniti should be held accountable and a recall should be issued for this problem. I will not stop until I can get through to someone that can help.

Filed Oct 4, 2023 · Acceleration, Electrical · GA

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.

Filed May 25, 2023 · Transmission · LA

My car has 60,000 miles on it and multiple mechanics as well as the Infiniti dealership tell me it needs a new transmission. $8,000. It will not shift above 2nd gear. I took the valve body and manifold out of the transmission and was surprised to find that the output speed sensor plug is actually a dumby plug that connects to nothing. I've had cars with hundreds of thousands of miles on them still driving with the same transmission they were born with. I've rebuilt a lot of engines, but never had to replace a transmission, especially not after 60,000 miles. Any, I searched the internet and noticed that it's a very common problem with this vehicle.

Filed Mar 31, 2023 · Transmission · FL

I was driving perfectly fine and i stopped at a red-light. I went to accelerate and the car wouldn't shift out of first gear and then check engine light came on. I pulled over and scanned the codes, it showed code p0500. After bringing to shop and reading thousands of different things from people who own the car online all said the same thing. Transmission valve body is shot. I almost got rear ended when i let off the gas because the engines rpms were so high casuing quick engine braking.

Filed Apr 25, 2022 · Transmission · GA

The vehicle would not shift above 3rd gear. I was driving down interstate and got off the exit and the shifting acted up. We were able to get home but this is clearly an issue that the federal safety agency has identified and this should be a recall. I have copied the link below.

Filed Jan 12, 2022 · Acceleration · GA

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. On a forum for Q50s another Infiniti owner said a dealer parts manager told them that Infiniti was aware there was a problem, and that the valve body was hard to come by and part of the delay was due to them redesigning the part to assure it didn't happen again. They suggested filing a case with Infiniti in case they were to issue some type of recall or TSB. He said out of the 750+ parts that were on backorder, his was #130 in line, and it still took over 2 months to receive. IF this is a known issue it is dangerous and should be addressed

Filed Jun 7, 2021 · Transmission · FL

I WAS DRIVING MY INFINITI Q50 and puled up to a light. When it turned green I proceeded when I noticed my check engine light comes. It won't shift past 3rd gear. it seems to be in limp mode but there was a tractor trailer barreling down on me. So I get to 35 MPH and ride the side of the road. Once I got home I did a search and apparently there are A LOT of issues with this transmission. Most indicated it was the valvebody and that it could cost upward of $2,500.00 plus there is a back order on them. This is my only car and can't have it tied up to long. I have an appointment to have it diagnosed this coming Wednesday, 06/09/2021. I can't drive it or I will burn up the transmission. If there is such a large problem I would think this would have a recall on it. My car only has 65, 624 miles on the clock. This needs to be addressed. I am hoping for a miracle when it gets diagnosed but with all the evidence out there about the bad transmission in these cars I am expecting the worse.