Mobile repair has a low barrier to entry: a pickup, a toolbox, and a Facebook page. That is fine until an uninsured stranger is under your $150,000 machine on your jobsite. Here is how to vet one before that happens.
1. Certification you can verify
ASE certification is the industry's standard proof that a technician has passed independent testing, and Master status in the medium-heavy truck series means passing the full battery of exams, not one. It is not the only signal of a good mechanic, but it is the one you can verify instead of taking on faith. Ask what certifications the person doing the work holds. A professional will not be offended; the other kind will get vague.
2. Licensed and insured, in writing
This one is about your liability, not theirs. An uninsured mechanic hurt on your site, or a botched repair that damages your machine, becomes your problem. Ask for proof of insurance and business licensing before the first job. Any legitimate operation can produce both without drama.
3. Listed rates, not vibes
The single best predictor of a fair invoice is whether the rates existed before your breakdown did. A professional outfit can tell you its labor rate, travel rate, and diagnostic fee on the phone, and quotes the job before the wrench turns. "We'll see how it goes" is how a $400 repair becomes a $1,400 invoice.
4. A warranty with a number on it
Everyone stands behind their work verbally. Ask what the warranty actually is: how many days, and on what. A specific answer, in writing on the invoice, separates a business from a side hustle.
5. Real diagnostic equipment
Modern diesels cannot be honestly diagnosed without a scanner that reads full codes and live data. Ask how they diagnose a derate or a no-start. If the answer is a story about experience instead of a method, expect your parts bill to fund the guessing.
6. Straight answers about coverage
A mobile mechanic who claims to cover everything, always, instantly, is telling you what you want to hear. A real one gives you a radius, realistic response expectations, and an honest no when a job belongs in a shop. Watch for the honesty as much as the answer.
The first-call test
You can run this whole checklist in one phone call: Who does the work and what are they certified in? Are you licensed and insured? What are your rates? What is the warranty? How will you diagnose it? Five questions, two minutes, and the vague answers eliminate themselves.
For the record, P&C's answers are on this site in plain sight: ASE Master Certified heavy and medium duty technician, licensed and insured, rates listed on the rates section of every page, 90-day warranty on covered repairs, and a $150 diagnostic hookup with full code and live data reads. That is the standard we think every outfit in this business should be held to, including us.