Rоyаl Jоkеr

Rоyаl Jоkеr is an offline-first troubleshooting workbench for anyone who reads their own trouble codes — DIY owners, shade-tree mechanics, used-car buyers, motorcycle and small-engine tinkerers, and auto-tech students.

Most apps hand you a code and a paragraph. This one hands you a procedure.

ENTER A CODE, GET A TREE
Every trouble code opens a branching diagnostic tree instead of a static list. Each node asks for one physical measurement you can actually take — resistance in ohms, voltage, fuel pressure in PSI, temperature, or a simple visual check. Tap the branch you observed, type the reading, and the tree prunes suspects node by node until it converges on a likely cause, the next part to test, and an honest confidence band — not a guess dressed up as certainty.

A SESSION THAT REMEMBERS WHERE YOU ARE
Diagnosis usually happens in a driveway, not at a desk. Sessions save their state, support explicit back and undo, let you bookmark a node, and pause or resume across app restarts. Every node has an inline note pad, so you can write down what you actually saw under the hood.

WORKS WITHOUT A SCANNER
The symptom browser is for the day your scan tool is still in the mail: "cranks but won't start", "misfire under load", "coolant loss with no puddle", "ABS light after a pothole". Each symptom fans out to the most probable codes and the tree worth starting.

CODE ENCYCLOPEDIA AND LIVE DATA
Search P0 through P3, plus B, C and U families. Each entry lists the systems affected, a severity tier (drive-now, fix-soon, park-it), common root causes, related codes and a jump straight into the matching tree. The PID reference covers fuel trims, O2 sensors, MAF, ECT, IAT, MAP, timing advance and misfire counters with plain-language meaning, typical ranges, units and a metric/imperial toggle.

GARAGE, READINESS AND REPORTS
Vehicle profiles (make, model year, engine, fuel type, transmission) filter which codes and trees actually apply and seed realistic normal ranges. The readiness explainer and drive-cycle coach walk you through which monitors are incomplete, why an emissions test fails, and the cycle sequence to complete them. Mileage and date reminders cover oil, filters, brakes, belts, spark plugs and inspection retest windows. Finished diagnoses roll into an archive and export as a clean PDF repair sheet: vehicle, code, tree path taken, readings logged, verdict and parts to test.

ON THE HOME SCREEN
A Glance widget pins the active diagnosis — vehicle, code, current node and next step — so you don't have to reopen the app with a wrench in your hand. An offline glossary covers 200+ automotive acronyms with instant search.

Everything works offline. The storage, background job queue and widget are plumbing you never see; what you get is a guided path from a raw code to a verified cause.

Rоyаl Jоkеr is a diagnostic aid, not a substitute for a licensed mechanic. Always follow your vehicle's service information and safe lifting procedures.