# 2026-16019: NHTSA Nixes Probe into Acura AWD Mystery Meltdown (7 words)

2026-16019, Denial of Motor Vehicle Defect Petition, is a Federal Register notice from Transportation Department, National Highway Traffic Safety Administration published 2026-08-06, effective 2026-08-06; PRIA reads it as touching household money (as of 2026-08-13).

- Canonical: https://policyrisk.com/federal-register/2026-16019
- As of: 2026-08-13
- Plain-text twin of the page above; the HTML and this file carry the same facts.

## Facts
- Document number: 2026-16019
- Title: Denial of Motor Vehicle Defect Petition
- Type: Notice
- Agencies: Transportation Department; National Highway Traffic Safety Administration
- Citation: 91 FR 50916
- Published: 2026-08-06
- Effective: 2026-08-06
- Comments close: not stated
- Significant: no
- Touches household money: yes
- Regulation identifier numbers: none
- Last updated: 2026-08-13

## In one line

NHTSA Nixes Probe into Acura AWD Mystery Meltdown (7 words)

## Summary

This notice sets forth the reasons for the denial of a petition, DP26-001, submitted by Mr. Christopher Mammarella (the Petitioner) to the Administrator of NHTSA (the "Agency") by a letter dated January 9, 2026, under 49 U.S.C. 30162 and 49 CFR part 552. The Petitioner requests the Agency initiate a safety defect investigation into allegations of a mechanical failure that results in the loss of All Wheel Drive (AWD) in certain Model Year (MY) 2021 to 2023 Acura TLX and MY 2022 to 2023 Acura MDX vehicles (the "Subject Vehicles") equipped with Acura's Super Handling All Wheel Drive (SH-AWD). As a result of the failure, these vehicles permanently lose the ability to transfer drive torque to the rear wheels effectively making them front wheel drive only. NHTSA's Office of Defects Investigation (ODI) has determined that the issues raised in the Petition are not likely to result in a finding that a defect related to motor vehicle safety exists. This determination is based on a technical review by ODI of available information, which included: (1) consumer complaints submitted by the petitioner; (2) consumer complaint information in the agency's databases; and (3) other relevant information in possession of the agency. As a result, further investigation of the issue raised by the Petition is not warranted and the Agency, accordingly, has denied the Petition.

## Effects PRIA read

- NHTSA Denies Defect Investigation: cost, high. On January 9, 2026 a petition (DP26-001) asked NHTSA to open a safety defect probe for certain MY 2021–2023 Acura TLX and MY 2022–2023 Acura MDX vehicles with SH-AWD. On August 6, 2026 NHTSA denied the petition and will not open a formal defect investigation or order a recall based on the informati…
- Loss of AWD Not Found To Cause Control Loss: benefit, low. NHTSA's Office of Defects Investigation concluded the reported shearing of splined shafts that stops rear torque transfer does not result in a loss of motive power or vehicle control for the subject vehicles. ODI reported it is not aware of any crashes attributed to the loss of SH-AWD in these vehi…
- No Driver Warning When AWD Stops Working: cost, medium. The SH-AWD system lacks any direct feedback to show real-time torque transfer, so the vehicle display can indicate power is going to the rear wheels even when the rear is not receiving torque. Operators often remain unaware of the condition until they encounter a low-friction surface or a technicia…
- Potentially Large Repair Costs If Failure Occurs: cost, high. According to the petitioner, when the splined shafts shear the transaxle and PTU must be replaced together, and the cost of that repair can range from $13,000 to $19,000. NHTSA reviewed consumer complaints and warranty data as part of its decision.

## Related documents

- [2026-19964](https://policyrisk.com/federal-register/2026-19964): The Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule III for Model Years 2022 to 2031 Passenger Cars and Light Trucks, 2026-09-30
- [2026-11072](https://policyrisk.com/federal-register/2026-11072): Federal Motor Vehicle Safety Standard No. 214; Side Impact Protection; Federal Motor Vehicle Safety Standard No. 305a; Electric-Powered Veh…, 2026-06-03
- [2026-08144](https://policyrisk.com/federal-register/2026-08144): Administrative Rulemaking, Guidance, and Enforcement Procedures, 2026-04-27
- [2026-05024](https://policyrisk.com/federal-register/2026-05024): Federal Motor Vehicle Safety Standards; Modernization of FMVSS No. 102 To Accommodate ADS-Equipped Vehicles, 2026-03-16
- [2026-05023](https://policyrisk.com/federal-register/2026-05023): Federal Motor Vehicle Safety Standards; Modernization of FMVSS No. 103 and FMVSS No. 104 To Accommodate ADS-Equipped Vehicles; Incorporatio…, 2026-03-16
- [2025-22674](https://policyrisk.com/federal-register/2025-22674): Public Hearing for Corporate Average Fuel Economy Standards: The Safer Affordable Fuel-Efficient (SAFE) Vehicle Rule III for Model Years 20…, 2025-12-12

## Sources
- [2026-16019 on federalregister.gov](https://www.federalregister.gov/documents/2026/08/06/2026-16019/denial-of-motor-vehicle-defect-petition)
- [2026-16019 as published (PDF)](https://www.govinfo.gov/content/pkg/FR-2026-08-06/pdf/2026-16019.pdf)

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Source: PRIA, https://policyrisk.com/federal-register/2026-16019 (as of 2026-08-13).