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…