Free Tools · No Email · Hill Country Diagnostics
Decode a code, scan a quote, check a recall, decide whether it's safe to drive — all of it free, most of it entirely inside your browser. We're a diagnostics-only business: our product is the truth about your car, so giving you the tools to demand one costs us nothing we were selling anyway.
Every tool follows the same house rule as every page on this site: what it proves, what a parts-changer will sell you, and the test that settles it. None of them replaces a real diagnosis — all of them make yours cheaper.
Three taps — lights, behavior, note — and a plain answer: keep driving, drive gently, or park it tonight.
What is that puddle leaking under the car? Color, smell, spot — nine fluid profiles, the drivability call, and what to refuse buying before the source is found.
Car won't start? Three rounds of see/hear/smell questions place you on one of 12 branches — with the free check and what NOT to buy.
Every dashboard icon, what it proves, the emergency call that goes with it, and what a parts-changer sells you.
Each rejection slip decoded: what the sticker actually says, the repair window it starts, and the honest fix.
One box over every code page, symptom, light, tool, town and FAQ answer. Live results, nothing uploaded.
Type any OBD-II code: what it proves, the guess-and-swap price, and the test that settles it.
No code, no light, just a problem? Plain-English pages for knocks, hums, slips, stalls and dead batteries.
VIN or year/make/model against the NHTSA database. Recall repairs are free at any dealer — never pay for one.
Full NHTSA decode of any 17-character VIN - engine, trim, factory, model year - with a check-digit warning that catches a typo before a parts counter does.
Oil, flushes, plugs, filters, battery — the honest interval, the inspection that beats the calendar, and the checker that runs your mileage against all of it.
Nineteen zero-tool checks to run before handing a stranger cash — each one says what a flag proves and what being wrong costs.
Paste any estimate; get the parts-cannon red flags in its own wording back, with the one question to ask per flag.
What alternators, cats, brakes and rebuilds really cost at an indie shop — plus the test that proves you need one.
Compare a repair quote against a diagnosis-first approach, on your numbers — not ours.
Repair quote and you are stuck on is it worth fixing? This decides it: repair vs. value, equity, payback per year, runway, trust — scored live on your numbers.
Thirty seconds, a handful of questions your mechanic has probably already answered — diagnosis or guess?
Enter your ZIP, get the honest drive-charge before anyone shows up. No phone tag, no surprise mileage math.
Exactly the document a customer receives — evidence, root cause, repair path. Read one before you trust one.
Flat rates for every service, printed on the site. The quote you see is the quote you pay.
Why the person diagnosing your car shouldn't be the one selling you the fix — the conflict, side by side.
Every result screen can carry your findings into the booking — code, quote, light, or checklist — so the visit starts with evidence already written down. Flat $150 mobile diagnostic. If we can't find the root cause, you don't pay the diagnostic fee. Period.
Fill in your vehicle info and service history, then print or save as PDF. Bring it to your next visit — Trent sees the full picture, not just the light.
We'll send a PDF copy — no spam, just the log sheet.
Canyon Lake, TX — Mobile Service
Vehicle Log
Oct 19, 2026
| DATE | MILEAGE | SERVICE | NOTES |
|---|---|---|---|
| — | — | — | — |
Prepared by Glass Box Diagnostics — honest mobile diagnostics for Canyon Lake & the Texas Hill Country
hello@glassboxdiag.com