OBD-II Error Codes
OBD-II (On-Board Diagnostics) codes are divided into four main sections, each prefixed with a letter. These four prefixes are as follow:
The number following the prefix tells you if the code is a generic OBD-II code or a manufacturer specific code. Generic codes start with a 0 (zero) while manufacturer specific codes start with a 1 (one).
The third number in the OBD-II code refers to any of the following sub-systems:
1 = Emission Management
2 = Injector Circuit
3 = Ignition/Misfire
4 = Emission Control
5 = Vehicle Speed and Idle Control
6 = Computer and Output Circuit
7 = Trans
8 = Trans
9 = SAE (reserved)
0 = SAE (reserved)
The last numbers in the code refer to a variable which is specific to the main problem.
For example, a Toyota specific OBD-II code P1129 would tell us that this is a Powertrain code, it is manufacturer specific because it has a 1. The third number (a 1 again) tells us it relates to the “Emission Management” sub-system, while the 29 refers to, in this particular example, the “Electric Throttle Control System”. This might not tell you exactly what the problem is but it certainly narrows it down.
To access these OBD-II codes you’ll need an OBD-II compatible scanner or reader, some software and a vehicle which is, in fact, OBD-II compliant. Most, but not all, vehicles built on or after 1996 should be OBD-II compatible.