Browse every trouble-code guide on this site with our OBD2 codes by category index. We grouped all 123 guides below by the vehicle system they belong to. If you already know your code, the All Codes A-Z index lists every code numerically.
Fuel & Air System Codes
- P0101
- P0102
- P0106
- P0113
- P0128
- P0170
- P0171
- P0172
- P0174
- P0175
- P0200
- P0299
- P0463
- P1101
- P2004
- P2006
- P2015
- P2096
- P2097
- P2187
- P2195
- P2196
- P2279
Misfire & Ignition Codes
Emissions System Codes
- P0036
- P0130
- P0131
- P0133
- P0134
- P0135
- P0136
- P0138
- P0140
- P0141
- P0155
- P0157
- P0400
- P0401
- P0402
- P0404
- P0410
- P0420
- P0421
- P0422
- P0430
- P0431
- P0440
- P0441
- P0442
- P0443
- P0446
- P0449
- P0451
- P0455
- P0456
- P0496
- P2033
- P2401
- P2402
- P2419
- P2422
- P2440
- P2442
Idle & Speed Control Codes
Computer & ECM Codes
- P0012
- P0013
- P0014
- P0116
- P0117
- P0118
- P0120
- P0121
- P0122
- P0325
- P0335
- P0340
- P0480
- P0500
- P0501
- P0521
- P0601
- P0606
- P2101
- P2111
- P2118
- P2135
- P2138
- P2172
- P2181
- 7E8
- 7EA
- 7E9
Transmission Codes
- P0700
- P0705
- P0715
- P0720
- P0730
- P0731
- P0732
- P0733
- P0734
- P0740
- P0741
- P0750
- P0753
- P0755
- P0760
- P0776
- P0780
Diesel & DPF Codes
Conclusion
That is the full set: all 123 trouble-code guides on this site, now browsable by system in this OBD2 codes by category index. Each system has its own section above: fuel and air, misfire, emissions, idle, computer, transmission, and diesel. Browse the section that matches your symptoms to compare related codes side by side.
If you already know your code, you can skip the browsing. The All Codes A-Z index lists every code numerically, and the Code Lookup tool jumps straight to the matching guide.
One safety note before you start: a steady check engine light means diagnose it soon. But a flashing check engine light means stop driving and see a mechanic in person. A flashing light signals a severe misfire that can overheat and destroy the catalytic converter in minutes.
Frequently Asked Questions About OBD2 Codes by Category
Quick answers to common questions about browsing trouble codes by system.
How do I know which system my code belongs to?
The code number itself is the best clue. P03xx codes point to misfires, and P07xx codes point to the transmission. P04xx codes cover emissions and EVAP, while P00xx and P01xx codes usually involve fuel, air, or engine timing. If the number does not make it obvious, match your symptoms to a section above.
What if my code is not listed?
We add new guides to the site on a regular schedule, so check back soon. Double-check that you typed the code exactly as your scanner shows it. One wrong digit points to a different guide. You can also use the search box at the top of the site to look for the exact code number.
Do these codes cover all cars?
Yes. Every code on this page is a generic OBD-II powertrain code. The same definition applies to any 1996 or newer car or light truck that uses OBD-II. Manufacturers can add extra codes of their own, and separate guides cover those where they exist.
Where do I start?
Start with the code from your scanner, then open its guide from the index above. Follow the diagnosis steps in order before replacing any parts. The code tells you which system reported a fault, not which part to buy. If your check engine light is flashing, skip the diagnosis and see a mechanic in person right away.