The First 10 Minutes of Diagnosis
This is the workflow good techs follow. It prevents expensive guesswork and gets you to the right next test faster.
Minute 0–2: capture the basics
- Exact complaint: when does it happen (cold, hot, idle, motorway, under load)?
- Any recent work: battery, intake, sensors, tuning, fuel changes.
- Scan everything: stored + pending codes.
Minute 2–5: freeze-frame + plausibility
- Record freeze-frame: RPM, load, coolant temp, trims, speed.
- Ask “does this make sense?”: e.g., lean code at idle suggests an air leak; lean at load suggests fuel delivery.
- Look for upstream causes: misfire/air leak can trigger catalyst or O2 codes.
Minute 5–10: choose one strong next test
Don’t shotgun five parts. Choose one test that can meaningfully rule a branch in/out.
- Air leak suspicion: smoke test intake/EVAP, check trims at idle vs cruise.
- Misfire under load: coil/plug swap test, inspect gaps, check fuel trims.
- Boost fault: compare target vs actual boost; check hoses, clamps, vacuum lines.
- Charging/electrical: battery voltage, alternator output, voltage drop tests.
If you’re not sure what test to pick, the AI tools are best when you paste freeze‑frame + symptoms.
Open AI Tools