A DTC is made up of 5 digits. The figure below demonstrates the composition of a OBD-II Diagnostic Trouble Code.
OBD-II Diagnostic Trouble Codes Explained
OBD-II codes consist of a number of parts. Below is a breakdown of what each digit of the code means:
First Character – System – The first character identifies identifies the system related to the trouble code.
P = Powertrain
B = Body
C = Chassis
U = Undefined
Second Digit – Code Type – The second digit identifies whether the code is a generic code (same on all OBD-II equpped vehicles), or a manufacturer specific code.
0 = Generic (this is the digit zero — not the letter “O”)
1 = Enhanced (manufacturer specific)
Third Digit – Sub-System – The third digit denotes the type of sub-system that pertains to the code
1 = Emission Management (Fuel or Air)
2 = Injector Circuit (Fuel or Air)
3 = Ignition or Misfire
4 = Emission Control
5 = Vehicle Speed & Idle Control
6 = Computer & Output Circuit
7 = Transmission
8 = Transmission
9 = SAE Reserved
0 = SAE Reserved
Fourth and Fifth Digits – These digits, along with the others, are variable, and relate to a particular problem.