DTC codes are five characters long. Each character in the DTC provides a different piece of information about the vehicle’s problem. 

The first character is always a letter. It indicates which control system has an issue, and has the following possible values and meanings:

  • P (powertrain) refers to the engine, transmission, fuel system, and associated accessories. 
  • C (chassis) refers to mechanical systems generally outside the passenger compartment such as steering, suspension, and braking.
  • B (body) refers to parts mainly found in the passenger compartment area. 
  • U (network) refers to the vehicle’s onboard computers and related systems.

The second character is a digit, typically 0 or 1, and shows whether or not the code is standardized. 

  • 0 indicates that the code is generic, standardized SAE (Society of Automotive Engineers) code. Generic codes are adopted by all cars that follow the OBD-II standard.
  • 1 indicates that the code is vehicle manufacturer-specific.These codes are unique to a specific car make or model and are typically less common. 
  • 2 or 3 are more rare and their meanings are dependent on the preceding letter of the code. Most of the time, 2 or 3 indicates that a code is manufacturer-specific, with only a few exceptions. 

The third character is also a digit, ranging from 1 to 8. This reveals the subsystem at fault.

  • 1 refers to the fuel or air metering system
  • 2 refers to the fuel or air metering injection system
  • 3 refers to the ignition system
  • 4 refers to the emissions system
  • 5 refers to the vehicle speed controls and idle control system
  • 6 refers to the computer output circuit
  • 7 and 8 indicate that the issue is transmission-related

The fourth and fifth characters are read together as a two-digit number between 0 and 99 known as the specific fault index. These characters identify the exact issue of the vehicle. 

If you are unsure about what your code means, check with your vehicle manufacturer or your vehicle manual for explanations.