OBD2 Error Codes Explained – What Your Check Engine Light Is Really Saying

That glowing check engine light can mean anything from a loose gas cap to a serious engine issue. OBD2 error codes help decode these warnings, giving drivers and technicians clear insight into what’s wrong.

What Are OBD2 Error Codes?

OBD2 error codes—also called Diagnostic Trouble Codes (DTCs)—are alphanumeric codes stored by the vehicle ECU when a fault is detected.

Code Structure

• P – Powertrain

• B – Body

• C – Chassis

• U – Network

Common OBD2 Codes

• P0171 – System Too Lean

• P0300 – Random Misfire

• P0420 – Catalyst Efficiency Below Threshold

How an OBD2 Scanner Helps

• Reads fault codes instantly

• Clears codes after repair

• Displays freeze-frame data

• Prevents unnecessary repairs

Conclusion

Understanding OBD2 error codes empowers you to fix issues faster and smarter.