Anatomy of the DTC: OBD2 Codes Explained

A DTC is made up of 5 digits. Knowing the composition of the code makes it is easier to trouble shoot a DTC without knowing the description of the code.

Here is a breakdown of what each digit of the code means.

[accordion auto_height=”false” ui_theme=”ui-smoothness”][accordion_panel title=”First Character – System“]The first character identifies identifies the system related to the trouble code.
P = Powertrain
B = Body
C = Chassis
U = Undefined [/accordion_panel] [accordion_panel title=”Second Digit – Code Type“]The second digit identifies whether the code is a generic code (same on all OBD-II equipped vehicles), or a manufacturer specific code.
0 = Generic (this is the digit zero — not the letter “O”)
1 = Enhanced (manufacturer specific) [/accordion_panel] [accordion_panel title=”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 [/accordion_panel] [accordion_panel title=”Fourth and Fifth Digits“]These digits, along with the others, are variable, and relate to a particular problem. [/accordion_panel] [/accordion]

Composition of a DTC

Types of DTC’s

There are two categories of DTC’s that apply to OBDII. They are listed below with Type A being the more severe.

Type A

Emissions related.
Requests illumination of the MIL after one failed driving cycle.
Stores a freeze frame DTC after one failed driving cycle.

Type B

Emissions related.
Sets a Pending Trouble Code after one failed driving cycle.
Clears a Pending Trouble Code after one successful driving cycle.
Turns on the MIL after two consecutive failed driving cycles.
Stores a freeze frame after two consecutive failed driving cycles.