Car Diagnostic Guides
Free, expert-written guides to help you understand your car's diagnostic system and fix problems yourself.
How to Use an OBD2 Scanner (Beginner Guide)
Step-by-step guide to reading and clearing diagnostic trouble codes with any OBD-II scanner tool.
Read guide →Check Engine Light — What It Means & What to Do
Why your check engine light is on, how urgent it is, and when you can safely keep driving.
Read guide →Understanding DTC Codes: P, B, C, U Explained
How to read OBD-II diagnostic codes — what each letter and digit means in plain English.
Read guide →Car Won't Start? Diagnostic Checklist
Systematic troubleshooting guide when your car won't start — from battery to fuel to ignition.
Read guide →How to Pass an Emissions Test (Even with Codes)
Prepare your vehicle for emissions inspection. Common fail reasons and how to fix them before your test.
Read guide →Complete DTC Code Guides by System
Comprehensive guides covering every diagnostic trouble code in a specific system — your one-stop OBD-II reference.
All Powertrain Fuel & Air DTC Codes (51 Codes)
Complete guide to every Powertrain Fuel & Air diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 51 codes →All Powertrain Ignition DTC Codes (31 Codes)
Complete guide to every Powertrain Ignition diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 31 codes →All Powertrain Emissions DTC Codes (28 Codes)
Complete guide to every Powertrain Emissions diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 28 codes →All Powertrain Engine DTC Codes (17 Codes)
Complete guide to every Powertrain Engine diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 17 codes →All Powertrain Transmission DTC Codes (16 Codes)
Complete guide to every Powertrain Transmission diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 16 codes →All Powertrain Computer DTC Codes (10 Codes)
Complete guide to every Powertrain Computer diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 10 codes →All Network Communication DTC Codes (9 Codes)
Complete guide to every Network Communication diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 9 codes →All Powertrain Fuel System DTC Codes (8 Codes)
Complete guide to every Powertrain Fuel System diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 8 codes →All Chassis ABS DTC Codes (7 Codes)
Complete guide to every Chassis ABS diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 7 codes →All Powertrain Speed & Idle DTC Codes (6 Codes)
Complete guide to every Powertrain Speed & Idle diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 6 codes →All Body Airbag DTC Codes (2 Codes)
Complete guide to every Body Airbag diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 2 codes →All Body Electrical DTC Codes (2 Codes)
Complete guide to every Body Electrical diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 2 codes →All Body Security DTC Codes (2 Codes)
Complete guide to every Body Security diagnostic trouble code — causes, symptoms, and step-by-step fixes.
View all 2 codes →