2014-2015 Q50; MIL ON WITH DTC P0720 AND MAY HAVE HARSH SHIFTING AND/OR LACK OF POWER SERVICE INFORMATION If DTC P0720 OUTPUT SPEED SENSOR is stored, follow the diagnostic procedure in the ESM. If the diagnosis leads to output speed sensor replacement, replace the control valve. Do NOT replace the output speed sensor. ï· - Refer to the ESM for control valve replacement: TRANSMISSION DRIVELINE> TRANSAXLE TRANSMISSION > 7 AT: RE7R01A > REMOVAL AND INSTALLATION > CONTROL VALVE TCM. HINT: The vehicle may also have harsh shifting and/or lack of power.
full bulletin at NHTSA ↗2015 INFINITI Q50 powertrain problems
moderate Owners of the 2015 INFINITI Q50 have filed 35 NHTSA complaints about the powertrain at roughly $2,500 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See powertrain across all vehicles →
Complaints
35
Recalls
0
Avg fix
$2,500
| Model year | powertrain complaints |
|---|---|
| 2014 Q50 | 16 |
| 2015 Q50 (this page) | 35 |
| 2016 Q50 | 4 |
| 2017 Q50 | 5 |
| 2019 Q50 | 5 |
What stands out
Of the 5 model years of INFINITI Q50 we track for powertrain problems, this one carries the most owner complaints on file — 35.
Owners have filed 35 powertrain complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering powertrain on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
TRANSMISSION & ENGINE AUTOMATED DATA COLLECTION AND DIAGNOSTIC REPORTING SERVICE INFORMATION To support proper diagnosis and to promote Fixed-Right-First-Time ? Infiniti may review CONSULT-III plus (CIII plus) data relating to vehicle operation and function to help with vehicle diagnosis and diagnostic validation. IMPORTANT: For transmission/engine repair or replacement, retailers are required to connect C-III plus and perform ?Diagnosis (All Systems)?. Performing C-III plus ?Diagnosis (All Systems)? is also required prior to contacting any Infiniti call center (i.e. TECH-LINE, PCC, or WCC) for diagnostic support or claim preauthorization. NOTE: For additional information regarding Automated
full bulletin at NHTSA ↗SERVICE INFORMATION If the glove box is removed for any reason (for example, installing an accessory kick plate, replacing an in-cabin microfilter, etc.), verify the trunk release power cancel switch operates normally after installing the glove box. See this bulletin for further detail.
full bulletin at NHTSA ↗SERVICE INFORMATION For QX60 Hybrid Vehicles, go to page 4. Q50, Q70, and M35 Hybrid Vehicles The internal combustion (IC) engine in the Q50, Q70, and M35 Hybrid vehicles is started using a high voltage motor that is integrated into the transmission. The high voltage motor gets its power from the high voltage Lithium-Ion (Li-ion) battery that is mounted between the trunk room and the rear seat. The Li-ion battery cannot be recharged using an external battery charger; therefore it is very important that the battery state of charge (SOC) is properly maintained during extended storage periods. Action must to be taken in order to prevent excessive discharge of the high voltage Li-ion battery dur
full bulletin at NHTSA ↗IF YOU CONFIRM All of the following: The FCW (Forward Collision Warning) malfunction is ON or reported to have been ON, and DTC C1A27 (ECD POWER SUPPLY CIRCUIT) is stored (Past or Current), and the brake fluid level is normal. NOTE: C1A27 is an ICC (Intelligent Cruise Control) DTC. ACTION Reprogram the ABS control unit (ABS) per the Service Procedure in this bulletin. - Part of the Service Procedure, step 20 on page 8, is a confirmation that reprogramming is needed to resolve the incident shown in Figure A and B on page 1. See this bulletin for further detail.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2015 Infiniti Q50 experiences a recurring transmission valve body failure affecting the Transmission Control Module (TCM). Owners describe sudden loss of power and inability to shift above third gear, often occurring at highway speeds with no warning. Diagnostic codes P0500 and P0720 appear after the failure, though many owners report no check engine light before the problem strikes.
The failure pattern is consistent: transmission enters limp mode or gets stuck in a single gear, forcing the vehicle to crawl at 30–40 mph. One owner's hard downshift from highway speed almost caused a rear-end collision. Several owners report intermittent shifting failures that worsen over time, sometimes resolving temporarily only to recur.
Repair costs are severe. Valve body replacement runs $2,200–$3,500 for the part alone, though most owners end up needing full transmission replacement at $4,000–$10,000. Parts are chronically back-ordered. Owners have found the TCM cannot be purchased separately. One owner discovered the output speed sensor plug is a dummy connection, raising design questions.
A 2019 Infiniti service bulletin exists (MC-10168892-0001), and a recall covers 2016 models, but Infiniti has not recalled the 2015 model despite extensive complaints. Multiple owners report this happens across 2014–2017 Q50s at varying mileage, with some failures as early as 56,000 miles. The failure is sudden and unpredictable, with zero warnings in most cases.
Same INFINITI Q50 powertrain reports on nearby years: 2014
Failure modes owners describe
Transmission valve body/TCM failure
The transmission valve body and/or Transmission Control Module (TCM) that sits on top of the valve body fails, causing the transmission to enter limp mode, inability to shift above third gear, or complete shift failure. Owners report this is a recurring defect affecting 2014–2017 Q50 models. One owner replaced the valve body at 99,000 miles; the failure reoccurred one week later, requiring full transmission replacement. Another owner had the valve body replaced at 60,000 miles and the issue recurred within two years.
When: Typically 56,000–115,946 miles; most commonly reported between 85,000–100,000 miles, though some failures occur as early as 60,000 miles.
Symptoms owners cite: Vehicle will not accelerate past 30–40 mph or stuck in third gear; Transmission refuses to shift or shifts with jerking and hard downshifts; Check engine light illuminates (sometimes delayed, sometimes none until restart); Vehicle enters limp mode or neutral-like condition; Odometer flashing reported in one case; Intermittent shifting failures (unpredictable); No warning before failure occurs
Codes mentioned: P0500 - Vehicle Speed Sensor A, P0720 - Output Speed Sensor Circuit
Repairs/costs cited: Valve body replacement quoted at $2,200–$3,500 for parts alone; complete transmission replacement quoted at $4,000–$10,000. Multiple owners report valve body is back-ordered by over one month. One owner found the output speed sensor plug to be a dummy plug connecting to nothing. Fluid entering TCM reported in one case. Part# 31705-x133a mentioned for one model year variant. TCM cannot be purchased separately; replacement requires entire valve body or transmission replacement.
Recalls/TSBs owners mention: Infiniti issued Service Bulletin MC-10168892-0001 (published November 2019) acknowledged by multiple owners. Recall NHTSA 24V-470 issued for propeller shaft on Q50/Q70, but one owner reported dealership parts shortage and delays for four months with no resolution. One recall mentioned for 2016 models but not 2015 models per one mechanic, though dealer has had to correct many 2015 models. No factory recall for valve body/TCM defect reported.
Speed sensor failure (electrical/corrosion)
Vehicle speed sensor or output speed sensor fails or becomes corrupted, triggering diagnostic codes. One owner discovered a dummy plug in the output speed sensor location that connects to nothing, suggesting potential design or manufacturing defect. Fluid contamination entering the TCM has been reported.
When: Can occur at any mileage from 56,000 miles onward; timing unpredictable.
Symptoms owners cite: Check engine light illuminates; Transmission unable to calculate speed properly; Vehicle stuck in one gear or limited shift range; Limp mode activation
Codes mentioned: P0500 - Vehicle Speed Sensor A, P0720 - Output Speed Sensor Circuit
Repairs/costs cited: One owner pulled valve body and manifold and discovered output speed sensor plug is a dummy plug that connects to nothing. One repair shop attributed failure to fluid breakdown and overheating due to transmission fluid not having adequate cooling capacity despite manufacturer claim of lifetime fluid.
Transmission fluid cooling inadequacy
Transmission fluid breaks down over time, reducing cooling capacity. Overheating causes TCM on valve body to fail prematurely, leading to valve body and transmission failure. Manufacturer claims transmission fluid is lifetime fluid, but owners report this is the root cause of the recurring valve body failures.
When: Failure typically occurs between 56,000–115,946 miles.
Symptoms owners cite: Transmission overheating (inferred from fluid degradation); Valve body/TCM failure following fluid breakdown
Repairs/costs cited: Transmission fluid replacement does not appear to prevent failure based on narratives. One transmission specialist indicated TCM could be welded back on but dealership replaces entire transmission instead.
Synthesized from 35 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 2 most recent
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…
While driving my Q50 on the highway at around 65mph my car automatically down shifted to 1st gear. It was a really hard shift, so hard I thought someone rear ended me. To down shift that quickly on the highway placed me in a very unsafe position. My car almost came to a complete stop without any notice to the vehicle behind me. Someone could have rear ended because I didn't hit my breaks. Thank…
Had powertrain trouble with your 2015 INFINITI Q50?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the powertrain problem on the 2015 INFINITI Q50?
It's a documented issue but not catastrophic. 35 complaints have been filed. Repairs average $2,500 and most owners catch it before it causes a breakdown.
At what mileage does the powertrain typically fail?
Based on the 35 complaints filed, powertrain issues most often appear around 83,038 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $2,500 for powertrain repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to powertrain?
No active recalls currently cover powertrain issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2015/INFINITI/Q50.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.