B
C
P
U
Interpreting the OBD2 Codes
An OBD2 scanner provides monitoring for various systems in vehicles. They include the engine control module, body, chassis, etc. When you use a scan tool to read the code, you can immediately tell which system has a fault based on how it appears. Here’s a breakdown for professionals and automotive enthusiasts.
The First Character (Letter)
All OBDII codes start with a letter that denotes the part of the vehicle that has a fault:
P – Powertrain: This includes the engine, transmission and all the associated accessories.
U – Network & Vehicle Integration: These functions are managed and shared by onboard computer systems.
B – Body: These parts are mainly found in the passenger compartment area.
C – Chassis: This covers mechanical systems and functions like steering, suspension, and braking.
The Second Character (Number)
The first letter is followed by a number. This number can only be ‘0’ or ‘1’:
0 – If it’s a ‘0,’ the code is a standardized (SAE) code, also known as a generic code.
1 – If it’s a ‘1,’ then you’re looking at a manufacturer-specific code.
The Third Character (Number)
This number denotes the particular vehicle system that has a fault. There are eight systems in total:
0 – Fuel and air metering and auxiliary emission controls
1 – Fuel and air metering
2 – Fuel and air metering (injector circuit)
3 – Ignition systems or misfires
4 – Auxiliary emission controls
5 – Vehicle speed control and idle control systems
6 – Computer and output circuit
7 – Transmission
The Fourth And Fifth Characters (Number)
The final part of a DTC (Diagnostic Trouble Code) is a two-digit number. This number defines the exact problem that you’re dealing with. It can be any number between 0 and 99. By reading this, you can use a manual or a professional diagnostic reader to check, clear, or erase the code from your vehicle’s system.
As you can see, a typical DTC has five characters in total, and each one of those characters gives it a description. The correct interpretation of these codes is vital for accurate car diagnostics.
Example:
Code: P0301
Description: Cylinder 1 Misfire Detected
Explanation:
P: Powertrain (the category of codes that include the engine, transmission, and associated accessories)
0: Standardized (SAE) codes. Codes starting with a “0” are standardized across all vehicle manufacturers. Codes starting with “1” are manufacturer-specific.
3: Refers to the area of the issue (in this case, “Ignition System or Misfire”)
01: Specific fault index. “01” refers to “Cylinder 1 Misfire Detected”.
Whether you’re a pro using a Bluetooth-enabled data diagnostic tool or a DIY with a basic scanner, understanding the meaning of these codes helps in effectively managing vehicle repairs and maintenance.
Disclaimer: Information is provided with diligence but without liability for inaccuracies or omissions. We are not liable for any direct or indirect damages resulting from the use of this information. Use at your own risk.
Cars:
Abarth, Alfa Romeo, Audi, Bentley, BMW, Cadillac, Chevrolet, Chrysler, Citroen, Dacia, Daewoo, Daihatsu, Dodge, Ferrari, Fiat, Ford, Foton, GWM, Honda, Hyundai, Isuzu, Iveco, Jaguar, Jeep, Jinbei, JMC, KIA, Lamborghini, Lancia, Land Rover, Lexus, Lotus, Mahindra/Renault, Maserati, Mazda, Mercedes, MG, Mini, Mitsubishi, Multicar, Nissan, Opel/Vauxhall, Peugeot, Porsche, Renault, Rolls-Royce, Rover, Saab, Samsung, Seat, Shuanghuan, Skoda, Smart, SsangYong, Subaru, Suzuki, Tata, Toyota, Volkswagen, Volvo, Yuchai and other.
OBD-II PIDs
OBD-II PIDs (On-board diagnostics Parameter IDs) are codes used to request data from a vehicle, used as a diagnostic tool. SAE standard J1979 defines many OBD-II PIDs. All on-road vehicles and trucks sold in North America are required to support a subset of these codes, primarily for state mandated emissions inspections. Manufacturers also define additional PIDs specific to their vehicles. Though not mandated, many motorcycles also support OBD-II PIDs. In 1996, light-duty vehicles (less than 8,500 lb [3,900 kg]) were the first to be mandated followed by medium-duty vehicles (between 8,500–14,000 lb [3,900–6,400 kg]) in 2005. They are both required to be accessed through a standardized data link connector defined by SAE J1962.
Trucks, Heavy Duty:
Agrale Bus, Alexander Dennis, Allison, Autosan, Chevrolet, Citroen, Dacia, Daf, Dennis Eagle, EvoBus Chasis, Fiat, Ford, Ford Cargo, Generic Bus Systems, Heuliez Bus, Hino, Hyundai, Irisbus Chassis, Isuzu, Isuzu Truck, Iveco, Iveco Trucks, Kamaz, Kia, King Long, Ladog, Lancia, Mahindra/Renault, MAN, MAN Bus Chassis, Mazda, Mercedes, Mercedes Truck, Mercedes Truck South America, Mitsubishi, Mitsubishi Fuso, Multicar, Nissan, Nissan Trucks, Opel/Vauxhall, Optare, Otokar, Peugeot, Plaxton, Renault, Renault Trucks, Scania, Scania Bus Chassis, Seat, Skoda, Solaris, Toyota, Trailers (Haldex, Knorr, Wabco), UAZ, VDL Berkhof, VDL Bova, VDL Bus & Coach, VDL Jonckheere, Volare, Volksbus, Volkswagen, Volvo Bus Chassis, Volvo Truck South America, Volvo Trucks and other.
Heavy-duty vehicles (greater than 14,000 lb [6,400 kg]) made after 2010, for sale in the US are allowed to support OBD-II diagnostics through SAE standard J1939-13 (around diagnostic connector) according to CARB in title 13 CCR 1971.1. Some heavy-duty trucks in North America use the SAE J1962 OBD-II diagnostic connector that is common with passenger cars, notably Mack and Volvo Trucks, however, they use 29 bit CAN identifiers (unlike 11-bit headers used by passenger cars).