2015 Infiniti Q50 Powertrain & Transmission Problems

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.

Transmission Control Body. Lost of speed during driving which put me in danger of being hit from behind on the highway. The car was scanned and came up the code P0500 and P0720.

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.

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.

The contact owns a 2015 Infiniti Q50. The contact stated while driving 40 MPH, the accelerator was depressed; however, the vehicle failed to shift into gear properly, with the check engine warning light illuminated. The vehicle was able to be restarted. The vehicle was taken to an independent mechanic, where it was diagnosed that the transmission valve body had failed, and the transmission needed to be replaced. The vehicle was not repaired. The dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 94,150.

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)

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.

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.

Transmission failure without warning!!

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.

I received a recall notice (folded information card) from Infinity in the mail in about August 2024 regarding Recall NHTSA 24V-470-R24A7. I also received an email from Infinity on August 28, 2024 with Subject "Your Q50 is due for Important recall repairs " and noted it stated Recall Code R24A7/R24A5: NHTSA 24V-470: Recall Description Q50/Q70 Prop Shaft. I contacted Infinity to schedule the repair and received a confirmed email service appointment for October 4th 2024. When I arrived at the dealership the service department told me they did not have parts but would change my oil and do other service for a fee. All I wanted was the recall fixed. In total I've been to the dealer 3 times and been always told that they have not received parts from the manufacturer. Today I called Infinity Consumer Affairs Department at 1-800-662-6200 and spoke to "Dennis". He did little but talk in circles and did nothing to provide information and when the recall would be fixed. Since I was getting no information and he was not listening or helping I told him I was ending the call and calling the NHTSA, which I did and spoke with Tyronda. Confirmation number for call she gave me is [XXX] for our call. After my repeated efforts and complaints, Infinity appears to have no interest on fixing the vehicle recall they first advised me of in August, only seemingly "going through the motions" as slow as possible. My car is not fixed after about 4 months and they have done nothing to contact me as to when it will be repaired. That is my complaint INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2015 Infiniti Q50. The contact stated that while driving at an undisclosed speed, the vehicle stalled. The contact was able to drive the vehicle off the highway and park the vehicle. The contact stated that the failure occurred while the contact was driving on a busy highway. The vehicle was towed to the dealer where it was diagnosed with transmission valve body failure. The contact was informed that the transmission valve body needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and a case was filed. The failure mileage was approximately 74,000.

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

My engine light came on at 115,946 miles causing my vehicle not to accelerate or shift properly which could have resulted in a accident. The vehicle was diagnosed at local Nissan dealership with code P0720 and P0500 stating vehicle need a transmission. Prior to this diagnose this vehicle was diagnose twice by a Nissan and Infiniti dealership concerning the shifting and acceleration issues but could not duplicate the issue at the time. I see where numerous car buyers are stating they’re having the same issues with the Infiniti brand at low miles and high miles.

The contact owns a 2015 Infiniti Q50. While driving at various speeds, the transmission was slow to shift. The vehicle failed to properly accelerate while depressing the accelerator pedal, and the check engine warning light remained illuminated. The vehicle was taken to a local transmission mechanic to be diagnosed, and it was determined that the gear ratio and speed sensor inside the transmission valve body were faulty, and that the valve body needed to be replaced. The valve body was replaced, and the failure was repaired; however, one week later, the failure reoccurred. The vehicle was taken back to the mechanic, and it was informed that the transmission needed to be replaced. The vehicle was not yet repaired. The manufacturer and local dealer were not contacted. The failure mileage was 99,000.

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.

$2000+ to fix but not recalled for Yet Way too more than thousand Infiniti Owners has had the same issue with Valve Body Code:P0720

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

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.

Transmission valve body failed and is a common problem for 2014-2016 I was on a busy road and the car threw check engine light and wouldn’t accelerate any more. I risked my safety and others because I was stopped in the middle of the road and lots of commuters passing by and the vehicle was fully registered and inspected by the state prior that happened but it’s a common problem that you’ll never know when it will fail.