This document supersedes SAE J2012 DEC2007, and is technically equivalent to ISO 15031-6:2010 with the exceptions described in 1.2. This document is intended to define the standardized Diagnostic Trouble Codes (DTC) that On-Board Diagnostic (OBD) systems in vehicles are required to report when malfunctions are detected. SAE J2012 may also be used for decoding of enhanced diagnostic DTCs and specifies the ranges reserved for vehicle manufacturer specific usage. This document includes:

1. a Diagnostic Trouble Code format.
2. b A description of the standardized set of Diagnostic Trouble Codes and descriptions contained in SAE J2012DA. The two most significant bytes of a DTC may be decoded according to two different lists; DTC Format Identifier 0x00 and 0x04.
3. c A description of the standardized set of Diagnostic Trouble Codes subtypes known as Failure Types contained in SAE J2012-DA (applies only when three byte DTCs are used).