On-board diagnostics (OBD) is an automotive term referring to a vehicle’s self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub-systems.
The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of on-board vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light or “idiot light” if a problem was detected but would not provide any information as to the nature of the problem.
Modern OBD implementations, commonly called OBDII or OBD2, use a standardized digital communications port to provide real-time data in addition to a standardized series of diagnostic trouble codes, or DTCs, which allow a person to rapidly identify and remedy malfunctions within the vehicle.
Opel Corsa C (X01; 2000) Utility Bakkie – pinterest.com
GM brands are among the best-known and most popular vehicles in the world. Their key brands include Cadillac, Chevrolet and GMC.
General Motors Key Brands
Chevrolet – GM’s line of Chevrolet vehicles is named for popular road racer Louis Chevrolet. Its popularity was based largely upon its value, durability, and performance.
Opel/Vauxhall – Opel, is a German automobile manufacturer which has been a subsidiary of Stellantis since 16 January 2021. It was owned by General Motors from 1929 until 2017 and by French automotive group PSA Peugeot Citroen, a predecessor of Stellantis, from 2017 until 2021. Vauxhall’s vehicle lineup is identical to that of Opel with the Vauxhall brand being exclusively used in the UK, the Channel Islands and the Isle of Man. Some Opel vehicles were sold in Australia under the Holden brand until 2020 and in North America and China under the Buick, Saturn, and Cadillac brands.
Cadillac – The Cadillac luxury car brand is one of GM’s most popular offerings. Established in 1902 with the founding of the Cadillac Automobile Company, the vehicle became a part of the General Motors portfolio in 1909.
Buick – In 1899, David Dunbar Buick established the Buick Auto-Vim and Power Company. The Buick offers entry-level access to luxury within the GM lineup. Buicks have long been included in GM’s portfolio, earning their spot there in 1908.
GMC – In World War II, GM added the GMC line of trucks to its portfolio. Today, the brand is still known for its full-size trucks.In addition to its full-size trucks, the GMC line also includes several sports utility vehicles.
Since its founding, Ford Motor Company has gone on to become one of the world’s largest and most profitable companies. As of 2020, there are three car brands operating under Ford Motor Company’s automotive group. These are Ford, Lincoln and Troller.
Ford – The original car brand owned by Ford Motor Company is, of course, Ford. Henry Ford was 39 years old when he founded Ford Motor Company in 1903.
Lincoln – Lincoln is the luxury vehicle division of Ford Motor Company. Named after Abraham Lincoln, the company was founded in 1917 by Henry M. Leland. The brand was acquired by Ford shortly after in 1922.
Troller – Troller is a Brazilian off-road vehicle manufacturer that was founded in 1995 by Rogério Farias.The brand was acquired by Ford Motor Company in 2007. Troller is most known for its flagship vehicle – the Troller T4 – which has been featured in numerous rally races around the world.
Brands No Longer Owned by Ford Motor Company
Jaguar & Land Rover – Ford acquired Jaguar in 1990 and Land Rover in 2000, but both brands were sold to Tata Motors in 2008.
Volvo – Volvo, a producer of Swedish luxury vehicles, was also part of Ford Motor Company’s automotive group for a period lasting from 1999 to 2010.
Mercury – Mercury, a former Ford division known for producing entry-level luxury cars, was discontinued in 2011.
All cars and light trucks built for sale in the United States after 1996 are required to be OBD-II compliant. There are five OBD-II protocol types in use:
J1850 PWM
J1850 VPW
ISO 9141-2
ISO 14230 KWP2000
ISO 15765 CAN
Each protocol differs electrically and by communication format.
ISO 15765 CAN protocol was developed by Bosch for automotive and industrial control. As of 2008 all vehicles sold in the US are required to implement CAN as one of their signaling protocols. As such, you can expect all vehicles that began first manufacture starting 2008 to be CAN enabled, and all other protocols abandoned from this point onwards.
The code reader or scan tool you use must be compatible with the vehicles specific protocol in order to communicate.
To determine which protocol your vehicle is using, you need to locate the Data Link Connector. It’s a 16-pin rectangular connector usually located below the steering column, behind the ash tray or within at least 3-feet from the drivers seat. It may also be located behind a snap off cover. The connector will not have all of the pins loaded. You can examine which pins are present to identify which protocol is being used. The diagrams below show all of the protocol pin positions.
After you determine your vehicles protocol, check your scan tools support list or look into the scan tools connector to see if the mating pins are present. If the mating pins are present it is a good sign but it is no guarantee that your tool will work.
SAE J1850 PWM
Pulse-Width Modulation — 41.6 kB/sec, standard of the Ford Motor Company
SAE J1850 PWM
Two wire differential
Pin 2: BUS+ signal
Pin 10: BUS- signal
Active bus state: BUS+ is pulled high while BUS- is pulled low
High signal voltage level: +5V (min/max 3.80 to 5.25)
Low signal voltage level: 0V (min/max 0.00 to 1.20)
Up to 12 message bytes, excluding frame delimiters
Bit Timing:
“1” Bit: Bus state active for 8uS (within 24uS bit period)
“0” Bit: Bus state active for 16uS (within 24uS bit period)
Start-Of-Frame: Bus state active for 48uS
SAE J1850 VPW
Variable Pulse Width — 10.4/41.6 kB/sec, standard of General Motors
SAE J1850 VPW
Single wire
Pin 2: BUS+ signal
Idle bus level is low
High signal voltage level: +7V (min/max 6.25 to 8.00)
Low signal voltage level: 0V (min/max 0.00 to 1.50)
Up to 12 message bytes, excluding frame delimiters
Bit Timing:
“1” Bit: Signal low for 128uS or high for 64uS
“0” Bit: Signal low for 64uS or high for 128uS Start-Of-Frame: Signal high for 200uS
ISO 9141-2 & ISO 14230 KWP2000
These protocols have an asynchronous serial data rate of 10.4 kbps. Communications happen on a single, bidirectional line without additional handshake signals.
ISO 9141-2 & ISO 14230 KWP2000
ISO 9141-2 is primarily used in Chrysler, European, and Asian vehicles.
Asynchronous serial communication at 10.4 Kbaud
Pin 7: K-line bidirectional for communication
Pin 15: L-line (optional) unidirectional for waking up the ECU
Idle signal levels are high
Signals are active pull-down to 0V (0.00 to 2.40)
High signal voltage level: +12V (min/max 9.60 to 13.5)
Up to 12 message bytes, excluding frame delimiters
Bit Timing:
UART signaling at 10.4K baud, 8 data bits, no parity, 1 stop
ISO 14230 KWP2000
Abbreviation is short for Keyword Protocol 2000
Asynchronous serial communication up to 10.4 Kbaud
Pin 7: K-line bidirectional for communication
Pin 15: L-line (optional) unidirectional for waking up the ECU
Idle signal levels are high Signals are active pull-down to 0V (0.00 to 2.40)
High signal voltage level: +12V (min/max 9.60 to 13.5)
Message may contain up to 255 bytes in the data field
Bit Timing:
UART signaling up to 10.4K baud, 8 data bits, no parity, 1 stop
ISO 15765 CAN
The CAN protocol was developed by Bosch for automotive and industrial control. As of 2008 all vehicles sold in the US are required to implement CAN.
ISO 15765 CAN
Controller Area Network (CAN bus) is a robust vehicle bus standard designed originally for multiplex electrical wiring within automobiles to save on copper.
High speed 250kbit/sec or 500kbit/sec
Pin 6: CAN high (CANH)
Pin 14: CAN low (CANL)
Dominant or active bus state: CANH driven high while CANL driven low
Recessive or idle bus state: CANH and CANL signals are not driven
CANH signal voltage level: 3.5V (min/max 2.75 to 4.50)
CANL signal voltage level: 1.5V (min/max 0.5 to 2.25)
