Onboard Diagnostics 2 (OBD2) Trouble Codes

The onboard diagnostics 2 (OBD2) system was designed for light and medium duty vehicles of 1996 and newer. The system uses diagnosis trouble codes (DTCs) to alert you when a vehicle experiences a malfunction. DTCs help vehicle mechanics and owners with a rich expertise in vehicle maintenance understand problems with the vehicle and where the root of the vehicle’s problem or problems may lie. Different DTCs represent specific problems in your vehicle. The DTCs that are required by law on all OBD2 systems are standardized and all vehicle manufacturers use the same common code list. This means the misfire code P0300 represents the same failure on a Chevy, Chrysler, Ford, or Toyota.

These codes were created by the Society of Automotive Engineers (SAE) to help vehicles comply with emission regulations. SAE is now called SAE International, and it is the professional organization that develops standards for automotive engineers.

Interpretation of OBD2 Codes

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.

Generic Powertrain Trouble Codes

Below are standard diagnostic trouble codes (DTCs) that are used by all manufacturers to identify vehicle problems. The codes provided below are generic codes that may not apply to all vehicles. Vehicle manufacturers may use manufacturer specific DTCs that differ slightly from the codes below.

Note: Due to the massive amount of codes in the listing, we have split them up into multiple pages. Choose the section of codes based on the first three characters of the code, e.g., P0171 is on the P01xx or P0100 through P0199 page):