Your check engine light just came on. Before you panic, let's understand what those OBD2 codes actually mean. What is OBD2? On-Board Diagnostics II (OBD2) is a standardized system in all cars manufactured after 1996. It monitors emissions-related components and stores Diagnostic Trouble Codes (DTCs) when issues are detected. DTC Code Structure Every code follows this format: P0XXX First letter : System P = Powertrain B = Body C = Chassis U = Network Second digit : Standard (0) or Manufacturer-specific (1) Third digit : Subsystem (1-8) Last two digits : Specific fault Most Common Codes Code Meaning Severity P0300 Random/Multiple Cylinder Misfire High P0171 System Too Lean (Bank 1) Medium P0420 Catalyst System Efficiency Below Threshold Medium P0442 EVAP System Leak (Small) Low P0128 Coolant Thermostat Below Threshold Medium DIY Diagnosis Steps Get a code reader - Basic OBD2 scanners start at $20 Plug into the OBD port - Usually under the dashboard, driver's side Read the code - Note both pending and confirmed…