Standardized Diagnostic Trouble Codes to SAE J 2012 (Diagnostic Trouble Codes)

Diagnostic Trouble Codes that can be read out by the ECM are standardized, which means that all manufacturers must use the same Diagnostic Trouble Codes.

The DTC is always a 5-character alphanumerical value, e.g. "P0100"  .

All PO  xxx codes are standardized. However, each manufacturer may use additional codes which go beyond the standardized ones. This is the case if the manufacturer has integrated additional functions in the ECM beyond those required by law, and these can also be diagnosed. These codes are referred to as P1  xxx codes, e.g. "P1100"  .

The first character (letter) of a code identifies the system which has input the code. A total of four system types are covered:

• B for body
• C for drive train
• P for drive 
• U for future systems.

The OBD II only requires the P code.

The second character represents the standard code (POxxx) or manufacturer code (P1xxx).

The third character indicates the system assembly from which a fault occurred.

These are:

PO 1  xx: Fuel

or and

PO 2  xx: air metering

PO 3  xx: Ignition system

PO 4  xx: Additional emission control systems

PO 5  xx: Speed and idle air control

PO 6  xx: Computer and output signals

PO 7  xx Transmission

The fourth and fifth characters represent the components or systems.