SUPPLEMENTARY INFORMATION:

1. Introduction

Any interested person may petition NHTSA to request that the Agency initiate an investigation to determine whether a motor vehicle or item of replacement equipment complies with an applicable motor vehicle safety standard or contains a defect that relates to motor vehicle safety. 49 U.S.C. 30162(a)(2); 49 CFR 552.3. Upon receipt of a properly filed petition, the Agency conducts a technical review of the petition, material submitted with the petition, and any additional information. 49 CFR 552.6. The technical review may consist solely of a review of information already in the possession of the Agency or it may include the collection of information from the motor vehicle manufacturer and/or other sources. Id. After conducting the technical review and considering appropriate factors, which may include, but are not limited to, the nature of the complaint, allocation of agency resources, agency priorities, the likelihood of uncovering sufficient evidence to establish the existence of a defect, and the likelihood of success in any necessary enforcement litigation, the agency will grant or deny the petition. See49 U.S.C. 30162(a)(2); 49 CFR 552.8.

2. Defect Petition Summary

In a letter dated January 9, 2026, the Petitioner requested that NHTSA “open a Preliminary Evaluation (PE) to investigate the metallurgy and design of the Power Take-off Unit (PTU) to transaxle splined connection” of the Subject Vehicles, to “review warranty claim data from American Honda Motor Co. for part numbers related to the PTU (Transfer Assembly) and the transaxle output shaft for the 2021-2023 model years,” and to “Direct Acura to issue a safety recall to remedy the defect, providing owners with a revised, high-strength component that can withstand the torque requirements of the 2.0L. 3.0L and 3.5L engines.” Mr. Mammarella supported his request by citing multiple online complaints in various user forums as well as 48 consumer complaints found on NHTSA's website.

Mr. Mammarella states that a critical mechanical failure occurs at the interface where the transaxle output shaft meets the PTU input shaft. The metal splines on the transaxle and PTU shafts strip or shear completely flat making torque transfer to the rear wheels impossible. Mr. Mammarella states that there is no clear indication to the driver that their vehicle is no longer functioning as an AWD vehicle. Mr. Mammarella alleges that fluid inspections by technicians frequently reveal “orange/discolored liquid” and metal shavings within the PTU housing. Because the damaged shafts are not available for replacement separately, the complete transaxle and PTU must be replaced when this failure occurs. Mr. Mammarella states that the cost of this repair can range from $13,000 to $19,000. NHTSA has based its decision on a review of the material cited by the Petitioner, pertinent information in NHTSA's databases, and other relevant information in possession of the agency.

3. Office of Defects Investigation Analysis

Most traditional AWD systems utilize mechanical and passive measures. These systems have the tendency to distribute torque along the path of least resistance, such as a wheel that has lost contact with the ground or is on a low friction surface such as ice. To compensate for this, many manufacturers use the brake system to redirect torque to the wheels with more traction. However, in this style of AWD system, a failed drive shaft or similar disconnection prior to the brakes often results in drive power being lost to the disconnected component. The consequence of this loss is the inability to maintain speed with surrounding traffic which increases the risks of collisions and injuries to the vehicle occupants.

The Subject Vehicles are built upon a platform that was designed primarily as Front Wheel Drive (FWD). The SH-AWD system functions more as a performance enhancement feature rather than a stability feature. Even if the SH-AWD is nonoperational, the vehicles retain full mobility via FWD. In addition, the Vehicle Stability Assist (VSA) remains functional, ensuring directional stability through traditional engine and brake-based traction control. As a result, although the condition raised by the Petitioner may degrade the vehicle's performance characteristics, there is insufficient information to indicate a potential unreasonable safety risk.

ODI reviewed 62 Vehicle Owner Questionnaires (VOQs) and several TREAD (Transportation Recall Enhancement, Accountability and Documentation) Field Reports alleging the loss of SH-AWD and its impact on the driving dynamics of the subject vehicles. During its analysis, ODI determined that the failure is localized to the mechanical interface between the FWD transaxle and the PTU. Specifically, the failure is the shearing or stripping of the interfacing splined ( printed page 50917) shafts between the FWD transaxle and the PTU, resulting in a permanent loss of torque transfer to the rear of the vehicle. Upon reviewing the technical details of SH-AWD, ODI has found that this failure does not result in any loss of motive power or lead to a loss of vehicle control.

Several complaints indicated that the operators were unaware of the mechanical fault until encountering a low friction surface or the condition was identified by a technician during routine maintenance. The SH-AWD system lacks any form of direct feedback for monitoring real time torque transfer to the rear wheels. Therefore, the system will continue to display information indicating power is being supplied to the rear wheels even when power is actually only supplied to the front wheels.

ODI's review did not identify sufficient evidence to indicate that the misinformation has presented a safety issue in the field. ODI did not identify any reports of loss of motive power or vehicle control that could be attributed to the loss of SH-AWD. ODI is not aware of any crashes involving the Subject Vehicles that resulted from the loss of SH-AWD.

The Agency has thoroughly assessed the material submitted by the Petitioner, consumer complaint information in NHTSA's databases, and other relevant information already in possession of the Agency. NHTSA does not believe that the issues presented by the Petitioner indicate the likelihood of a safety related defect that would warrant a formal investigation. After full consideration of the available information, and in view of NHTSA's enforcement priorities, the Petition is denied.

(Authority: 49 U.S.C. 30162(d) and 49 CFR part 552; delegation of authority at 49 CFR 1.95(a).) ^[1]

91 FR 50916