Free · HTML + printer-friendly PDF
P0420
Catalyst System Efficiency Below Threshold
Ranked causes with percentage bars, a step-by-step flowchart, normal vs. failed test values, pro tips and safety warnings — everything on one sheet. Open the HTML on any phone, tablet or laptop, or print the PDF for the bay wall.
Free · Open on any device or print it
VIN DECODER
VIN Decoder: 17-Position Reference Guide
VIN decoder reference: all 17 positions explained, including country, manufacturer, model year, plant and serial number. Free reference sheet.
Free · Open on any device or print it
DLC PINOUT
OBD-II DLC Pinout & Quick Checks (16-Pin)
OBD-II DLC pinout: all 16 pins mapped and grouped by power, ground, CAN and legacy protocols, with quick electrical checks including the pin 6 and 14 CAN resistance test. Free reference sheet.
Free · Open on any device or print it
RPO & BUILD CODES
RPO & Build Codes Reference (GM, Ford, Stellantis)
Where to find the build label on GM, Ford and Stellantis vehicles and how to read the factory option codes (RPO) for engine, transmission and axle. Free reference sheet.
Free · Open on any device or print it
TIRE SIDEWALL
Tire Sidewall Decoder: Size, Load & Speed Ratings
Tire sidewall decoder: size, aspect ratio, load index, speed rating, traction grades and the DOT date code explained. Free reference sheet.