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 illuminates the MIL and sets 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 code's origin.

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