Thomas J. Hardwell
Master Diesel Mechanic, ASE Certified
About Thomas
Thomas J. Hardwell is a Master Diesel Mechanic and ASE Certified technician with 20 years of hands-on experience in heavy-duty engine diagnostics. He has spent his career diagnosing and repairing Class 8 commercial trucks across major US fleets, specializing in Cummins, Detroit Diesel, Volvo, PACCAR, and International engine platforms.
Throughout his career, Thomas has logged over 40,000 hours of diagnostic work on heavy-duty diesel engines, from roadside fault-code triage to full engine overhauls. He holds ASE T2 (Electrical/Electronic Systems), T4 (Brakes), and T6 (Suspension and Steering) certifications, and has been a contributing technical reviewer for fleet maintenance publications.
Credentials & Expertise
- ASE Certified — Medium/Heavy Truck series (T2, T4, T6)
- 20 years heavy-duty engine diagnostics experience
- Specialist in SAE J1939 and SAE J1587 fault code protocols
- Expert in Cummins, Detroit Diesel, Volvo, PACCAR, International engine platforms
- Former fleet maintenance supervisor for a Top 50 US carrier
- Technical contributor to fleet maintenance industry publications
Role at DTC Hub
Thomas serves as the lead technical editor and subject-matter expert for DTC Hub. He reviews all fault code definitions and diagnostic procedures for technical accuracy, ensures severity classifications align with real-world fleet data, and translates SAE standard terminology into plain-language guidance that drivers and mechanics can act on at the roadside.