Vehicle towed in with a crank, no start condition. Initial checks: - Battery low → supported with jump pack (no change) - Engine fires on ether → mechanical condition OK Scan results: - P1604 – Start ability Malfunction First Direction: Fuel System - Fuel sample taken → contaminated (kerosene smell) - Filter removed → debris + metal present - External clean diesel supply connected → still no start - No fuel movement during cranking Re-test & Re-think Second scan: - P062D – Injector Driver Circuit Performance - P0627 – Fuel Pump Control Circuit Now we shift from fuel supply → control issue ⚡ The Actual Fault Using OEM data: - Low voltage at ECU injector driver pins (+BD1 / +BD2) - Relay control side OK - But no power feed to the circuit 👉 Root cause:25A fuse missing ✅ Fix - Installed correct fuse - Voltage restored at ECU - Codes cleared - Engine starts normally Takeaway Contaminated fuel was a real issue… but not THE issue Diagnose the system, not the symptom This could’ve easily turned into: - Pump replacement - Injector replacement - ECU replacement Instead… it was a missing fuse. 👇 Discussion At what point would you have shifted from fuel diagnosis → electrical control?

This group is for mechanics, workshop owners, and serious DIYers who want to get better at diagnostics — together. No ego. No parts swapping. No guessing. We’re here to share real fault codes, real testing, and real-world thinking from the workshop and the garage. We’re kicking things off with a weekly Diagnostic Challenge — a place to break down scenarios, compare process, and sharpen our method. There’s no “perfect” answer. Only better thinking. Before the first challenge drops, comment below: - Tech / Owner / DIY - What you want to improve most in diagnostics Let’s build something solid