Recall 25V521 affects 32 2025-2026 Mack Anthem (An) and Pioneer Pr (4) trucks for a steering-guidance malfunction. Free repair at any franchised Mack dealer.
Mack is recalling 32 2025-2026 Anthem (An) and Pioneer Pr (4) vehicles because the dynamic steering and oversteer guidance feature can malfunction and cause loss of steering control. A loss of steering control increases crash risk, and Mack dealers will complete the recall repair free of charge.
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What's wrong?
The 2025-2026 Mack Anthem (An) and Pioneer Pr (4) trucks in this recall use dynamic steering with an oversteer guidance feature. That software-controlled feature is meant to help correct the truck when it detects oversteer, the condition where the rear of the truck starts to rotate more than intended. Parameter P1HF9 controls that feature.
On affected trucks, Mack found that the feature can correct for oversteer and then keep correcting in the opposite direction. That back-and-forth correction creates steering oscillations. Instead of settling the truck, the system can create a control issue that requires the driver to intervene, and the NHTSA filing ties the defect to loss of steering control. Mack traced the problem to insufficient validation across vehicle variations.
The filing does not identify a dashboard warning, sound, or other owner warning sign before the unwanted correction starts. Mack's fix is to turn off the oversteer guidance feature, which removes this specific steering control risk.
Who's affected?
Covers Anthem (An) and Pioneer Pr (4) trucks across the 2025 and 2026 model years, all tied to the same oversteer guidance software parameter.
| 2025 Mack Anthem (An) | steering system |
|---|---|
| 2026 Mack Pioneer Pr (4) | steering system |
| 2025 Mack Pioneer Pr (4) | steering system |
| Units affected | 32 |
| Field incidents | NHTSA has logged 1 field incident to date. |
A matching year and model does not guarantee inclusion. Check your VIN to confirm whether your specific truck is included.
What's the safety risk?
A loss of steering control increases the risk of a crash. Until the fix is installed, drive cautiously, keep extra space around the truck, and schedule service soon. Mack's fix disables the oversteer guidance feature through an OTA update or dealer service. Repair is free at any franchised Mack dealer.
What should I do?
- Check your VIN to confirm your 2025-2026 Mack Anthem (An) or Pioneer Pr (4) is included in this recall.
- Contact a franchised Mack dealer to schedule the free update that disables the oversteer guidance feature and addresses the steering-control malfunction.
- Install the OTA update if Mack provides it for your truck, or have the dealer perform the update.
- Bring the recall notice if you have it, and reference recall number 25V521 when you call.
- Limit driving until the update is complete, and contact the dealer before any trip if the truck shows steering-control problems.
What happens at the repair
At the dealer, a Mack technician disables the oversteer guidance feature by applying the recall update. Mack can also deliver the same disablement through an over-the-air (OTA) update, so the service desk can tell you whether your truck needs a visit or has already received it. The update is free under the recall. Mack used its general reimbursement plan on file, so if you already paid for a related steering or software repair, bring documentation and ask the service desk how to submit the claim.
| Reimbursement | Reimbursement available |
|---|
Timeline
| August 11, 2025 | NHTSA published the recall |
|---|---|
| August 15, 2025 | Dealer notification began |
| August 15, 2025 | Dealer notification ended |
| August 15, 2025 | VIN-searchable in NHTSA's database — Check your VIN to see whether this recall applies to your specific vehicle. |
| August 21, 2025 | Owner notification mailed |
| October 5, 2025 | Interim owner notification (was planned for this date) |
Frequently asked questions
What is recall 25V521?
Recall 25V521 covers 32 2025-2026 Mack Anthem (An) and Pioneer Pr (4) vehicles with a dynamic steering and oversteer guidance feature that can malfunction and cause loss of steering control. Mack will disable the oversteer guidance feature by over-the-air update or dealer service for free.
What should I do if my 2025-2026 Mack Anthem (An) or Pioneer Pr (4) is on this recall?
Check your VIN to confirm your specific vehicle is included in recall 25V521. If it is, contact a franchised Mack dealer to arrange the oversteer guidance disablement, or confirm whether the over-the-air update has already completed. Reference Mack recall number SC0483 when you call.
Is the recall repair free?
Yes. Federal recall law requires the manufacturer to repair the defect at no cost. Mack will disable the oversteer guidance feature through an over-the-air update or dealer service free of charge.
What is the safety risk in recall 25V521?
The safety risk is loss of steering control. Mack reported that the dynamic steering and oversteer guidance feature can malfunction, and a loss of steering control increases the risk of a crash. If your VIN is included, arrange the free recall repair.
When were owners notified about recall 25V521?
Mack mailed owner notification letters on August 21, 2025. If you bought the vehicle used or never received the letter, check your VIN to confirm whether your specific truck is included, then contact a franchised Mack dealer and reference recall number SC0483.
More information
| NHTSA campaign page | nhtsa.gov/vehicle-recalls/25V521000 |
|---|---|
| Mack customer service | 1-800-866-1177 |
| NHTSA recall # | 25V521 |
| NHTSA recall # (full) | 25V521000 |
Source documents
-
Download Quarterly Report (PDF) - Download Recall Investigation Document (PDF) (PDF)
- Download Owner Notice (PDF)
- Download Recall Report (PDF)
- Download Recall Acknowledgement (PDF)
This article is generated from NHTSA's primary recall filings and reviewed against the source on May 19, 2026. RecallNotify does not paraphrase NHTSA's consequence language; that text is reproduced as written above. Editorial standards →