Interpreting OBDII Codes

[wolfman]

OBDII Codes are broken down into 4 catagories Body, Chassis, Powertrain, and UNetwork codes. OBDII codes can only be retrieved with scantool. SOME codes can also ONLY be retrieved by a scantool equiped with manufacturer specific proprietary software. Codes retrieved will be in a 5 space format {X X X X X} interpret the 5 spaces thusly:

First digit:
B= Body Code
C= Chassis Code
P= Powertrain Code
U= Network Code

Second digit:
0=SAE Standard Code
1= Manufacturer Specific Code

Third digit:
1=Fuel and Air metering
2=Fuel and Air metering (injectors)
3=Ignition system (missfiring)
4=Auxcillary Emission Controls
5=Vehicle Speed & Idle Controls
6=Computer Output Circuit
7=Transmission
8=Transmission
9=Reserved
0=Reserved

Fourth and Fifth digit(s)
00-99=Identifies specific fault

OBDII GM code lists follow this post