Rear Brake Modulators May Short Circuit

Affected vehicles (2)

Component / system

Defect

Mack Trucks, Inc. (Mack) is recalling certain 2025-2027 Pioneer (4) and 2026-2027 Anthem (4) vehicles. The rear brake modulators may have unprotected electrical connectors that can short circuit and lead to a loss of the anti-lock brake system (ABS) and electronic stability control (ESC).

Risk / consequence

A loss of anti-lock brakes and electronic stability control increases the risk of a crash or injury.

Remedy

Dealers will inspect the rear brake modulator electrical connectors, install a protective cover, and replace the rear brake modulators, as necessary, free of charge. Owner notification letters were mailed June 8, 2026. Owners may contact Mack's customer service at 1-800-866-1177. Mack's number for this recall is SC0494. Vehicle Identification Numbers (VINs) involved in this recall will be searchable on NHTSA.gov beginning April 30, 2026.

Chronology of events

1. Jan 12, 2026

   January 12, 2026: Service Market quality report opened due to a rising number of field reports received for vehicles logging diagnostic code C10C256.

2. Mar 2, 2026

   March 2, 2026: Engineering begins an investigation into the root cause. Field reports are inconclusive on the issue leading to the DTC.

3. Mar 10, 2026

   March 10, 2026: Supplier technical support visits a vehicle and discovers an unprotected electrical connector on a rear brake modulator.

4. Mar 16, 2026

   March 16, 2026: The product Safety Office launches a potential safety investigation for a loss of ABS/ESP from an unprotected modulator connector.

5. Mar 23, 2026

   March 23, 2026: Product Safety Evaluation Committee reviews investigation information and determines that more information is needed to understand the customer effect.

6. Apr 6, 2026

   April 6, 2026: Product Safety Evaluation Committee reviews investigation information and recommendations escalation to Product Safety Committee.

7. Apr 14, 2026

   April 14, 2026: Product Safety Committee requests more information about driver experience when the fault occurs.

8. Apr 16, 2026

   April 16, 2026: Product Safety Committee determines that a product safety issue exists and decides to initiate a recall. There have been 5 field reports, 4 warranty claims, and no accidents or injuries reported related to this issue. Field reports and warranty claims are linked to 6 unique VINs. The following is the breakdown of claims per build period: 2025: September-2, October-3 2026: Feb-1

Notification schedule

Dealer notification

Apr 30, 2026 - Apr 30, 2026 No Dealers

Owner notification

Jun 22, 2026 - Jun 22, 2026 Phased Recall