2023 Mack Md Problems
Owner-reported complaints filed with NHTSA, grouped by component
Data refreshed
What this page shows
Everything below is an owner-reported complaint submitted to NHTSA about the 2023 Mack Md, grouped by the component NHTSA recorded on the report. These are not confirmed defects, and they are not recalls. NHTSA does not verify most reports before publishing them, and a category with more reports in it is not evidence that a part is defective.
Complaints are reports submitted by owners and drivers to NHTSA. They are not verified and do not establish that a defect exists.
Reports by component
Ranked by how many owner reports name each component category
- Engine133.3%
- Fuel system133.3%
- Powertrain (other)133.3%
Percentages are of component mentions. A single complaint can name more than one component, so these do not sum to the total complaint count.
Each component in detail
What the reports in each category say, in the owners' own words
Engine
Reports naming the engine itself — including stalling, misfires, oil consumption, cooling and internal engine components.
From owner reports, verbatim
COMPONENTS THAT FAILED: Multiple systems failed in a connected chain. (1) The DPF aftertreatment differential pressure sensor — a CONFIRMED manufacturing defect per Cummins recall T7186/T7187 (Jan 2026). (2) The Allison automatic transmission — catastrophic internal failure: torque converter destroyed, flexplate warped and cracked, metal fragments throughout. (3) The transmission control unit wiring (circuits 143/123) reversed at the factory. The DEF sensor in the same aftertreatment system also failed back in Dec 2023, 14 months before the DPF symptoms — proving a system-wide defect. All failed components and repair invoices are available for inspection upon request. SAFETY RISK: After the dealer declared repairs complete, the truck was driven under 10 miles when the engine entered SEVERE DERATE (limp) mode WITHOUT WARNING, with four alerts firing at once including aftertreatment and transmission failures. Sudden, drastic power loss on a heavy commercial truck in live traffic is extremely dangerous — it can leave the vehicle unable to maintain highway speed, risking a collision with surrounding vehicles. The dealer released the truck in this hazardous state with no warning. CONFIRMED BY MULTIPLE SHOPS: Yes. The problem was reproduced and confirmed repeatedly — by the authorized dealer, by an independent transmission shop, and at final repair. The fault returned within 30 minutes on one visit and within 10 miles on another. INSPECTED BY: The authorized dealer and an independent service center inspected the vehicle and failed components. Documentation is available. WARNING SIGNS: Yes. Warning lamps appeared from the very first visit in Feb 2025 — transmission code P071A and high soot codes 1981/1922. They persisted for NINE MONTHS without proper repair, until the transmission catastrophically failed in Nov 2025. The vehicle was out of service over 45 days.
Too few reports in this category for a page of its own — they appear in the full complaint list.
Fuel system
Reports naming fuel storage or delivery — tanks, pumps, lines, injectors and fuel leaks.
From owner reports, verbatim
COMPONENTS THAT FAILED: Multiple systems failed in a connected chain. (1) The DPF aftertreatment differential pressure sensor — a CONFIRMED manufacturing defect per Cummins recall T7186/T7187 (Jan 2026). (2) The Allison automatic transmission — catastrophic internal failure: torque converter destroyed, flexplate warped and cracked, metal fragments throughout. (3) The transmission control unit wiring (circuits 143/123) reversed at the factory. The DEF sensor in the same aftertreatment system also failed back in Dec 2023, 14 months before the DPF symptoms — proving a system-wide defect. All failed components and repair invoices are available for inspection upon request. SAFETY RISK: After the dealer declared repairs complete, the truck was driven under 10 miles when the engine entered SEVERE DERATE (limp) mode WITHOUT WARNING, with four alerts firing at once including aftertreatment and transmission failures. Sudden, drastic power loss on a heavy commercial truck in live traffic is extremely dangerous — it can leave the vehicle unable to maintain highway speed, risking a collision with surrounding vehicles. The dealer released the truck in this hazardous state with no warning. CONFIRMED BY MULTIPLE SHOPS: Yes. The problem was reproduced and confirmed repeatedly — by the authorized dealer, by an independent transmission shop, and at final repair. The fault returned within 30 minutes on one visit and within 10 miles on another. INSPECTED BY: The authorized dealer and an independent service center inspected the vehicle and failed components. Documentation is available. WARNING SIGNS: Yes. Warning lamps appeared from the very first visit in Feb 2025 — transmission code P071A and high soot codes 1981/1922. They persisted for NINE MONTHS without proper repair, until the transmission catastrophically failed in Nov 2025. The vehicle was out of service over 45 days.
Too few reports in this category for a page of its own — they appear in the full complaint list.
Powertrain (other)
Powertrain reports that are not specifically the engine or transmission — driveshafts, axles, transfer cases and differentials.
From owner reports, verbatim
COMPONENTS THAT FAILED: Multiple systems failed in a connected chain. (1) The DPF aftertreatment differential pressure sensor — a CONFIRMED manufacturing defect per Cummins recall T7186/T7187 (Jan 2026). (2) The Allison automatic transmission — catastrophic internal failure: torque converter destroyed, flexplate warped and cracked, metal fragments throughout. (3) The transmission control unit wiring (circuits 143/123) reversed at the factory. The DEF sensor in the same aftertreatment system also failed back in Dec 2023, 14 months before the DPF symptoms — proving a system-wide defect. All failed components and repair invoices are available for inspection upon request. SAFETY RISK: After the dealer declared repairs complete, the truck was driven under 10 miles when the engine entered SEVERE DERATE (limp) mode WITHOUT WARNING, with four alerts firing at once including aftertreatment and transmission failures. Sudden, drastic power loss on a heavy commercial truck in live traffic is extremely dangerous — it can leave the vehicle unable to maintain highway speed, risking a collision with surrounding vehicles. The dealer released the truck in this hazardous state with no warning. CONFIRMED BY MULTIPLE SHOPS: Yes. The problem was reproduced and confirmed repeatedly — by the authorized dealer, by an independent transmission shop, and at final repair. The fault returned within 30 minutes on one visit and within 10 miles on another. INSPECTED BY: The authorized dealer and an independent service center inspected the vehicle and failed components. Documentation is available. WARNING SIGNS: Yes. Warning lamps appeared from the very first visit in Feb 2025 — transmission code P071A and high soot codes 1981/1922. They persisted for NINE MONTHS without proper repair, until the transmission catastrophically failed in Nov 2025. The vehicle was out of service over 45 days.
Too few reports in this category for a page of its own — they appear in the full complaint list.
Higher-selling and older vehicles accumulate more reports. Counts are not failure rates and are not directly comparable between vehicles that sold in very different numbers.
Elsewhere on this vehicle
Data sources
- NHTSA Office of Defects Investigation — owner-reported complaints and the components recorded on them
Data on this page last refreshed .