OBD & Scan Tool History
From early onboard diagnostics through OBD-II, CAN and modern scan tools.
What was OBD-I?
Short answer: OBD-I refers to the first generation of on-board diagnostics required in California starting with 1988 model-year vehicles.
OBD-I refers to the first generation of on-board diagnostics required in California starting with 1988 model-year vehicles. Systems varied by manufacturer, with different connectors, codes and procedures.
What was the purpose of the California Air Resources Board's OBD rules?
Short answer: The California Air Resources Board (CARB) required on-board diagnostics to help detect emissions-related malfunctions.
The California Air Resources Board (CARB) required on-board diagnostics to help detect emissions-related malfunctions. The goal was to keep vehicles running cleanly and alert drivers to problems.
When did OBD-II become mandatory?
Short answer: OBD-II became mandatory for all 1996 model-year cars and light trucks sold in the United States.
OBD-II became mandatory for all 1996 model-year cars and light trucks sold in the United States. It standardized diagnostic connectors, codes and data, making generic scan tools possible.
How did the J1962 connector standardize diagnostic access?
Short answer: Before OBD-II, automakers used many different diagnostic connectors.
Before OBD-II, automakers used many different diagnostic connectors. SAE J1962 defined a standard 16-pin connector for OBD-II vehicles, so one cable could plug into any compliant vehicle.
How did SAE J1979 standardize diagnostic data?
Short answer: SAE J1979 defined the standard diagnostic test modes for OBD-II, such as reading live data, stored codes and freeze frame.
SAE J1979 defined the standard diagnostic test modes for OBD-II, such as reading live data, stored codes and freeze frame. It ensured generic scan tools could request emissions-related data from any compliant vehicle.
How did SAE J2012 standardize trouble codes?
Short answer: Before OBD-II, codes were manufacturer-specific.
Before OBD-II, codes were manufacturer-specific. SAE J2012 defined a standard format for diagnostic trouble codes, giving P0 codes and other categories common meanings across makes.
What were early OBD-II communication protocols?
Short answer: Early OBD-II protocols included SAE J1850 PWM, SAE J1850 VPW, ISO 9141-2 and ISO 14230 (KWP2000).
Early OBD-II protocols included SAE J1850 PWM, SAE J1850 VPW, ISO 9141-2 and ISO 14230 (KWP2000). Different manufacturers used different protocols until CAN became mandatory.
When did CAN become required for OBD-II?
Short answer: In the United States, CAN (ISO 15765) became required for OBD-II communication on 2008 model-year vehicles.
In the United States, CAN (ISO 15765) became required for OBD-II communication on 2008 model-year vehicles. It became the standard protocol for diagnostics.
What was the GM ALDL connector?
Short answer: The Assembly Line Diagnostic Link (ALDL) was GM's diagnostic connector used before OBD-II.
The Assembly Line Diagnostic Link (ALDL) was GM's diagnostic connector used before OBD-II. Technicians could retrieve flash codes by jumping terminals.
What were flash codes?
Short answer: Flash codes were blink patterns from the check engine light that indicated trouble codes.
Flash codes were blink patterns from the check engine light that indicated trouble codes. They were used on many OBD-I vehicles.
What was the GM Tech 1?
Short answer: The Tech 1 was a GM dealer scan tool used in the 1980s and 1990s.
The Tech 1 was a GM dealer scan tool used in the 1980s and 1990s. It plugged into the ALDL connector and displayed codes and data.
What was the GM Tech 2?
Short answer: The Tech 2 was GM's dealer scan tool introduced in the mid-1990s.
The Tech 2 was GM's dealer scan tool introduced in the mid-1990s. It supported OBD-II and was used for many years.
What was the Snap-on MT2500?
Short answer: The Snap-on MT2500, often called the "Red Brick," was a popular aftermarket scan tool in the 1990s.
The Snap-on MT2500, often called the "Red Brick," was a popular aftermarket scan tool in the 1990s. It used cartridges to support different vehicles.
When did generic OBD-II scan tools appear?
Short answer: Generic OBD-II scan tools appeared as OBD-II became required on U.S. vehicles from the 1996 model year.
Generic OBD-II scan tools appeared as OBD-II became required on U.S. vehicles from the 1996 model year. Because the standards defined common connectors, codes and data, one tool could read emissions-related information on many makes.
Why was SAE J2534 pass-thru programming adopted?
Short answer: SAE J2534 defines a standard interface for reprogramming vehicle modules using a PC and a pass-thru device.
SAE J2534 defines a standard interface for reprogramming vehicle modules using a PC and a pass-thru device. It was adopted so independent shops could reprogram emissions-related modules without buying a dealer tool for every brand.
General guidance only. Follow the vehicle and tool manufacturer's procedures, and confirm vehicle coverage on the tool maker's list before buying.