2015 INFINITI Q50 Powertrain (other) Problems

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.

NHTSA ID

11756528

Incident

Aug 8, 2026

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.

NHTSA ID

11750490

Incident

Jul 7, 2026

The valve body on these cars are useless. Driving down a highway and cant shift out of 3rd gear almost had a car re-end me. Today I am driving and the ECU is not responding I see the check engine light on then I'm like not again. This would be the 3rd valve body I replaced. First I replaced the whole transmission thinking that is what I needed and advised that the valve body and the transmission are one. Yet no they come in parts. Anyways today I am waiting to get home, but the car is not reading my key fob why? Then the ECU and code U0100 is popping up. Something new and turns the car off. The shifting that happen earlier was just a light bulb of I already knew what is wrong. I felt the car shift with a hunch so I looked at my dash board and saw the check engine light again and was like not again. Please not again. Now on the dash board I see AWD and chassis issue. Then online I am told electrical problem and or ECU module not reading correctly. Like what is up with these push to starts. They are becoming a headache. I need to know just why I am replacing my valve body now for the 4th time???? This all can cause an accident that my car randomly slows down.

NHTSA ID

11737881

Incident

May 14, 2026

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.

NHTSA ID

11731441

Incident

Apr 14, 2026

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.

NHTSA ID

11718621

Incident

Feb 12, 2026

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.

NHTSA ID

11684079

Incident

Aug 16, 2025

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.

NHTSA ID

11683201

Incident

Aug 24, 2025

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.

NHTSA ID

11681660

Incident

May 1, 2025

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.

NHTSA ID

11672262

Incident

Jul 9, 2025

Mileage

94,150 mi

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)

NHTSA ID

11664950

Incident

May 26, 2025

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.

NHTSA ID

11663166

Incident

May 22, 2025

Air bag light suddenly said “passenger airbag off”. Don’t have to brake to switch gears. Steering at times feels a bit off.

NHTSA ID

11655792

Incident

Apr 21, 2025

Transmission failure without warning!!

NHTSA ID

11655236

Incident

Mar 14, 2025

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.

NHTSA ID

11649578

Incident

Mar 20, 2025

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.

NHTSA ID

11649291

Incident

Mar 7, 2025

Valve body goes bad after a few hundred miles every time. fluid enters the tcm causing it to go bad. the tcm could be welded back on but dealer just replaces the whole transmission

NHTSA ID

11647122

Incident

Aug 11, 2015

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)

NHTSA ID

11628333

Incident

Aug 28, 2024

Valve body went out with 89k miles and had to get transmission replaced.

NHTSA ID

11606745

Incident

Aug 6, 2022

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.

NHTSA ID

11606722

Incident

Mar 17, 2023

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.

NHTSA ID

11586114

Incident

Apr 25, 2024

Mileage

74,000 mi

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

NHTSA ID

11586096

Incident

Apr 24, 2024

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.

NHTSA ID

11582897

Incident

Apr 8, 2024

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.

NHTSA ID

11548342

Incident

Sep 28, 2023

$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

NHTSA ID

11538467

Incident

Aug 1, 2023

The contact owns a 2015 Infiniti Q50. The contact stated that while driving approximately 50 MPH, the vehicle began to overheat and smoke was present coming from under the hood. After stopping to inspect the vehicle the contact opened the hood and flames were present in the engine compartment. The contact immediately extinguished the flames using water. The vehicle was later towed to the local dealer. The cause of the failure was not yet determined. The contact indicated that prior to the fire the vehicle had also experienced transmission shifting failures and the front driver's side and passenger side seat belts were locked in the retracted position and could not be used. The cause of the failures was not determined. The manufacturer was not notified of the failures. The failure mileage was 80,000.

NHTSA ID

11537944

Incident

Mar 10, 2023

Mileage

80,000 mi