2015 Infiniti Q50 acceleration problems

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 Apr 15, 2026 · Acceleration, Transmission · GA

The transmission speed sensor has failed needs a new valve body. It seems like a very common problem with this car and it’s a $3000 fix according to my mechanic. I think there needs to be a recall issued considering everybody on this website is reporting the same problems.

Filed Aug 26, 2025 · Acceleration, Electrical · CA

The car just slowed down super fast on freeway almost got rear ended. It would not go past 3rd gear. Poor acceleration. Could have caused a huge accident. I got it diagnosed and they said it is valve body/speed sensor/tcm and they said this is a COMMON problem for 2015 Q50. I replaced this part 2 years ago and here we go again. Shop diagnosed and said this tcm (transmission control module which is in the transmission) but they have to change whole transmission. Everything happened all the sudden then check engine light came on.

Filed Aug 19, 2025 · Acceleration, Transmission · TX

i’m reporting issues with the valve body on a 2015 Q50. I have had to replace the valve body already at cost of $1700. Many others have had same issue as this is a common defect with the TMC part. This needs to be addressed as a recall.

Filed Aug 19, 2025 · Acceleration, Electrical · CA

P07200 code came up, transmission is no good because of a cheap sensor that's impossible to fix. seems to be very common and very inconvenient

Filed Jun 4, 2025 · Acceleration, Transmission · TX

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)

Filed Mar 20, 2025 · Acceleration, Steering · LA

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.

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 Sep 9, 2024 · Acceleration · AL

P0500 vehicle speed sen/cir P0720 a/t veh speed sen/ circuit-or- output speed sensor P1574 ascd vhcl apps sensor - or lcc vhl spd sen (icc models) My safety was put at risk when the vehicle hesitated and stop changing gears while traffic was behind me. The vehicle was inspected by a local dealership which was Nissan and also Infiniti including a transmission shop named ammco. There were no warning lights that would indicate the vehicle was failing until April the 5th

Filed Aug 6, 2024 · Acceleration · KY

The valve body went bad at 164k miles. Im not the only one. On all the forums and fb groups im on, there are hundreds of valv bodys going bad on the q50s for this general area of the year. On my facebook group i have seen 4 people in the past 2 days with theirs going out. Code p0720. Mine is being hauled to the shop right now so i dont have paperwork of replacement at this time for a few days