AI Damage2021 Mack MD: common problems
The maker issued 112 service bulletins for this year. Details by component below, with sources.
Key figures
- Technical service bulletins (TSB)
- 112
Components owners complain about
| Component | Owner complaints | involving a crash | Technical service bulletins (TSB) |
|---|---|---|---|
| Engine and cooling | 0 | 0 | 50 |
| Electrical system | 0 | 0 | 20 |
| Powertrain | 0 | 0 | 19 |
| Fuel system | 0 | 0 | 9 |
| Equipment | 0 | 0 | 6 |
| Suspension | 0 | 0 | 6 |
| Engine | 0 | 0 | 5 |
| Service brakes | 0 | 0 | 3 |
| Wheels | 0 | 0 | 3 |
| Fuel/propulsion system | 0 | 0 | 2 |
| Vehicle speed control | 0 | 0 | 2 |
| Communication | 0 | 0 | 1 |
| Electronic stability control | 0 | 0 | 1 |
| Lane departure | 0 | 0 | 1 |
Comparison
What to check before buying
- Engine and cooling. Radiator and fan after a frontal hit, coolant level and condition, overheating.
- Electrical system. Scan all modules, test the battery and alternator, inspect connectors near the impact zone.
- Powertrain. Shift quality under load, harsh shifts, transmission codes, CV joints.
- Fuel system. Fuel smell, leaks, rough running, fuel-system codes.
Manufacturer service bulletins
Bulletin titles as filed with NHTSA.
- CBR - Mack Chassis - Through Shaft Bearing Retainer Breakage On Mack Carriers
- CBR - Mack Carrier Nut Adhesive Change
- TSB - Cable, Gear Selector, Replacement
- CBR - No Start Condition After Over the Air Programing
- CBR - Mack DEF Level (UQLS) Sensor Troubleshooting Guide - US17+OBD16 Emissions to US22+OBD2023 (DOES NOT…
CBR - Mack DEF Level (UQLS) Sensor Troubleshooting Guide - US17+OBD16 Emissions to US22+OBD2023 (DOES NOT APPLY TO AN(4) and PR(4)).
- CBR - When an OTA (Over-The-Air) job starts to program the VECU blocks the starter relay out, if the job…
CBR - When an OTA (Over-The-Air) job starts to program the VECU blocks the starter relay out, if the job ends in a Critical failure, the vehicle will remain in Safe State.
- CBR - To correct the MID136 SID 66 FMI 7 fault code the latest Bendix VCP file will need to downloaded
- CBR - A significant GPS reporting issue is affecting fleet operations, with trucks maintaining back-office…
CBR - A significant GPS reporting issue is affecting fleet operations, with trucks maintaining back-office communication but failing to transmit GPS location data.
- Mack DEF Level (UQLS) Sensor Troubleshooting Guide - US17+OBD16 Emissions and Newer
- Vehicles Equipped With a Common Rail Fuel System - Aftermarket Secondary Fuel Filters, Important…
Vehicles Equipped With a Common Rail Fuel System - Aftermarket Secondary Fuel Filters, Important Information On Approved Filters - US17+OBD16 toUS21+OBD23
- If oil dilution is suspected refer to the applicable CBR solution below
∙ CBR-659Mack Chassis - Oil Diluted With Fuel; Fuel In Oil, Diagnostic Information - All Emissions, All Model Years
- Frame lean can be caused by several seemingly isolated possibilities
The two most common are suspension and frame assembly issues.
NHTSA lists 112 bulletins for this year; the 12 newest are shown here.
Other years of this model
Questions and answers
What are the most common problems with the 2021 Mack MD?
There are no owner complaints in the NHTSA data for this year; the data comes from 112 manufacturer service bulletins.
How many service bulletins (TSB) were issued for the 2021 Mack MD?
NHTSA lists 112 manufacturer service bulletins for this year. A bulletin tells dealers how to diagnose or fix a known issue; it is not a recall.
Should I buy a 2021 Mack MD from a US auction?
Owner complaints describe defects, not crash damage. Before bidding, check the components listed above and review the lot photos: VinWind builds a report of visible and hidden damage by VIN.
Other 2021 models
Read also
Sources: public NHTSA data (USA): service bulletins and owner complaints; YouTube: links to videos credited to their authors. Complaints are owner statements not verified by NHTSA, and describe defects rather than crash damage. Data updated 2026-11-04.