OBD II System Codes

OBD II System Code P0301 Format Explained

The OBD II system monitors different areas of the vehicle. If a problem or conflict is detected, the system will illuminate the MIL and set a code in the PCM's memory. An OBD II code is an alphanumeric code containing a letter as its first digit followed by a series of numbers. Let's have a closer look at the meaning of these digits.

1. The first digit uses an acronym to indicate the codes origin.

  • P indicates powertrain.
  • B indicates body.
  • C indicates chassis.
  • U indicates network.

2. The second digit (0) indicates whether this is a generic (SAE) code or (1) for a manufacturer specific code.

3.The third digit indicates the area of the vehicle at fault. A 3 indicates an ignition system misfire, a 7 would indicate a problem with the transmission. There are several.

4. Both the fourth and fifth digits (01) indicate the specific area. The code in the illustration indicates a misfire with the (01) #1 cylinder.