78 of the
740 complaints filed about the Infiniti Q50
are about the transmission —
11% of everything owners reported.
The worst model year for it is 2015.
78
Complaints
11%
Share of all complaints
3
Crashes
1
Fires
Transmission & Drivetrain complaints by model year
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 complaint #11756528 — an unverified report by a vehicle owner.
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 complaint #11750490 — an unverified report by a vehicle owner.
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 complaint #11737881 — an unverified report by a vehicle owner.
While operating the vehicle under normal driving conditions, the engine experienced a significant loss of power and reduced acceleration. The issue is believed to be related to turbocharger failure within the engine system. The loss of power created a safety concern, particularly when attempting to merge into traffic and maintain highway speeds. The vehicle did not respond as expected when acceleration was needed, which could increase the risk of an accident in certain driving situations. The problem has been confirmed by a dealership service department, and the vehicle is currently available for inspection. The diagnosis indicates that the turbochargers require replacement. Prior to the failure, there were limited warning signs. Any warning indicators were either minimal or appeared shortly before the issue became noticeable. The failure occurred at approximately 107,000 miles. Based on publicly available information, similar failures have been reported on this vehicle model, suggesting a possible pattern related to the turbocharger system.
NHTSA complaint #11732566 — an unverified report by a vehicle owner.
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 complaint #11731441 — an unverified report by a vehicle owner.
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.
NHTSA complaint #11722204 — an unverified report by a vehicle owner.
Shortly after purchasing the vehicle, I began experiencing serious performance issues. While driving, the vehicle suddenly lost power, would not accelerate properly, and warning lights appeared on the dashboard. The vehicle eventually shut off while in operation. The vehicle was inspected by a dealership, which initially stated there were no issues. However, the problem continued and worsened. The vehicle was then inspected by an authorized Infiniti dealership, where technicians identified a consistent knocking noise coming from the engine. The dealership indicated that the noise is consistent with internal engine damage and recommended further inspection and likely engine replacement. The issue developed very shortly after purchase, and there were no prior indications that the vehicle had been damaged or misused. The sudden loss of power and engine failure created a potential safety hazard, especially while driving in traffic, as the vehicle was unable to accelerate and could have led to a dangerous situation. The vehicle is currently available for inspection, and the issue has been confirmed by a certified dealership. The cause of the failure is currently under further evaluation.
NHTSA complaint #11721157 — an unverified report by a vehicle owner.
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 complaint #11718621 — an unverified report by a vehicle owner.
Filing this complaint regarding a safety-related defect involving the turbocharger system on my 2018 INFINITI Q50. The vehicle has approximately 46,000 miles and is 8 years old. INFINITI/Nissan has acknowledged through its own Technical Service Bulletins (TSBs) that turbocharger failure on 2016–2018 Q50 3.0T vehicles is a known defect. Nissan’s documentation identifies issues such as turbo oil seal leaks, reduced engine power, smoke, and potential catastrophic engine failure, and provides an extended warranty of up to 10 years or 120,000 miles due to the safety risks associated with sudden power loss. My vehicle experienced turbocharger failure consistent with these known defects, resulting in loss of engine power, which presents a serious safety hazard, particularly during highway driving, merging, or intersections. Sudden loss of propulsion increases crash risk and endangers vehicle occupants and others on the road. In some cases, turbo failure can occur with little or no warning, further increasing risk. The failure was confirmed by INFINITI/Nissan service departments, and the vehicle remains available for inspection. CarMax insurance approved the engine repair, acknowledging mechanical failure; however, they declined to approve turbocharger repair specifically because INFINITI has issued a known TSB and extended warranty covering turbo failure, deferring responsibility to the manufacturer. Despite the vehicle being within the extended warranty limits, Nissan denied coverage, claiming the vehicle has a “branded title.” This claim is unsupported by VIN reports, the loan originator, and CarMax’s own title search prior to leasing all confirm the title is not branded. Nissan has provided no documentation supporting its assertion. Nissan N.A. reviewed and closed the matter despite the known safety defect and lack of evidence for the title claim. Represents a safety-related defect and improper denial of a manufacturer-recognized safety remedy, warranting NHTSA review.
NHTSA complaint #11709489 — an unverified report by a vehicle owner.
I am the owner of a 2017 INFINITI Q50 purchased in 2019. My vehicle has suffered three separate turbocharger failures in four years: 2021 (~75,000 miles): turbocharger failure; replaced under my extended warranty (~$6,000 authorization). 2023 (~98,000 miles): turbocharger failure; replaced again under extended warranty (~$6,000 authorization). 2025 (143,000 miles): diagnostic confirms another turbocharger failure; quoted $8,900 out of pocket because my extended warranty has expired. These failures follow the classic symptoms of excessive exhaust smoke and MIL illumination that INFINITI has explicitly linked to premature turbocharger bearing wear in the February 2025 “limited emission warranty extension” for 2016–2018 Q50 and 2017–2018 Q60 vehicles. INFINITI’s bulletin states the company “is conducting a warranty extension to Full Useful Life (FUL) of 10 years or 120,000 miles” for select turbo assemblies where white smoke/oil-leak with MIL-on requires turbo replacement, and explains the reason as “possibility that the turbocharger bearing may leak engine oil internally due to premature wear.” INFINITI’s public owner-facing campaign page likewise describes this extension and its terms (10 years/120,000 miles), including reimbursement for qualifying prior repairs. Infiniti Assist While my current mileage exceeds 120,000 miles, my car has required two full turbo replacements before 100,000 miles and now requires a third at 143,000 miles. This pattern evidences a latent defect present well within the extension period and is consistent with the failure mode INFINITI acknowledges. They have offered no help and only assume 50% responsibility when they 100% have manufactured defective and poorly labored parts.
NHTSA complaint #11685053 — an unverified report by a vehicle owner.
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 complaint #11684079 — an unverified report by a vehicle owner.
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 complaint #11683201 — an unverified report by a vehicle owner.
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 complaint #11681660 — an unverified report by a vehicle owner.
I received a check engine light will driving which is now indicated as code P0720 and P0500. The car refused to shift past 3rd gear and began to sputter and would not allow me to go past 25mph disrupting the flow of traffic.
NHTSA complaint #11673542 — an unverified report by a vehicle owner.
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 complaint #11672262 — an unverified report by a vehicle owner.
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 complaint #11664950 — an unverified report by a vehicle owner.
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 complaint #11663166 — an unverified report by a vehicle owner.