A code is a starting point, not an answer. P0420 doesn't mean you need a catalytic converter; it means the computer saw something it didn't like downstream. We read live data, freeze-frame, and mode 6 results, test the suspected component, and tell you what's actually wrong — and what it will cost to fix — before anything gets replaced.
Signs you need check engine light diagnostics
- Check engine light on or flashing
- Light comes and goes
- Failed emissions or inspection
- Poor fuel economy with no obvious cause
- Reduced-power or limp mode
What we do on site
- Full-system scan including ABS, airbag, transmission, and body modules
- Review freeze-frame and live data for the fault
- Test the suspected sensor, circuit, or component directly
- Give you a written finding and a firm repair quote
- Clear codes after the repair and verify readiness monitors
Doing this in a driveway
Scan tools are portable. Every diagnostic we do at a shop, we do in your driveway.
Parts we use
None for the diagnosis; whatever the fault requires after.
Pricing: A flat diagnostic fee, credited toward the repair if we do it. Every job is quoted in writing before we start, and there's no upsell — how our pricing works.
FAQ
Check Engine Light Diagnostics: common questions
The parts store read my code for free — why pay for a diagnosis?
Because the code tells you which system tripped, not which part failed. An oxygen sensor code can be a bad sensor, an exhaust leak, a vacuum leak, or a wiring problem. Diagnosis is what keeps you from buying parts that don't fix it.
Is a flashing check engine light an emergency?
Yes. A flashing light means an active misfire that's dumping raw fuel into the catalytic converter. Stop driving and call us; we'll come to the car.
Will you clear the light so I can pass inspection?
Clearing the light resets the readiness monitors, which will fail inspection anyway. We fix the cause; then the monitors set and the car passes.