In the past, trouble code numbers varied between manufacturers, years, makes and models. OBD II requires that all vehicle manufacturers use a common Diagnostic Trouble Code (DTC) numbering system. Since the generic listing was not specific enough, most manufacturers came up with their own DTC listings which are called manufacturer specific codes. Both generic and manufacturer specific codes are 5-digits. The numbers can be decoded as follows:
The first digit is a letter which identifies the function of the device or circuit which has the fault. This digit can be either:
The second digit is either a 0 or 1 and indicates whether the code is generic or manufacturer specific.
The third digit represents the specific vehicle circuit or system that has the fault. Listed below are the number identifiers for the powertrain system.
The last 2 digits indicate the specific trouble code.
On OBD II vehicles, there are 2 types of DTC's: Stored and Pending. For a DTC to become Stored, certain malfunction conditions must occur. The condition(s) required to Store codes are different for every DTC and vary by vehicle manufacturer.
In order for some DTC's to become Stored, a malfunction condition has to happen more than once. If the malfunction conditions are required to occur more than once, the potential malfunction is called a Pending DTC. The DTC remains pending until the malfunction condition occurs the required number of times to make the code stored. If the malfunction condition does not occur again after a set time the pending DTC will be cleared.