Onboard diagnostic standardization wasn't always guaranteed

Deciphering the varied trouble codes of vehicle diagnostics once required the persistence and multilingual fluency of Jean-François Champollion, the Frenchman who cracked the Rosetta Stone.

But that changed with the advent of standardized vehicle diagnostics. Onboard diagnostic system II ended what was essentially a dark age for the repair of vehicles with combustion engines. The industry began phasing in the onboard diagnostic system II in 1994 and now is in the early stages of developing a similar technology for electric vehicles.

Onboard diagnostic tools are crucial for speedier and more accurate service and repair. Passenger car drivers have certainly benefited from the technology, but commercial fleet owners have arguably made the most of standard onboard diagnostics as they can more quickly and easily collect information about the operations of their entire fleet. Commercial fleets typically include vehicles from multiple brands and with different specifications.

"You can buy a Freightliner truck with a Freightliner engine, you can buy it with a Cummins engine, you can now buy a Cummins natural gas" engine, said Mike Roeth, executive director of the North American Council for Freight Efficiency. "OBD II was really important to trucking because you had multiple different engines, different transmissions, and it was a way to help make that happen more efficiently."

The first onboard diagnostic computer systems entered passenger cars in the late 1960s, but the technology ramped up in the 1980s. For years, this first generation of diagnostics, now known as onboard diagnostic system I, was not standard. Mechanics were forced to retain different onboard diagnostic tools for different ports and decipher varied codes from different automakers. Some onboard diagnostic system I scan tools had multiple cables to connect to different ports.

The proprietary nature of the ports and codes also funneled drivers to dealerships rather than independent repair shops.

The standardization of onboard diagnostics began with an unlikely source — the California Air Resources Board, which wanted to use the technology to reduce vehicle emissions. As with EV requirements today, California's mandates drove innovation across the nation in the 1980s and 1990s.

CARB mandated onboard diagnostic systems in all vehicles starting with the 1988 model year, but it did not mandate specific standards, creating an unnavigable web of cables and codes. Additionally, what later became known as onboard diagnostic system I was not fully effective because it was "limited to monitoring only a few" emissions-related components, and the monitors were not calibrated to a specific emissions performance, according to a CARB fact sheet.

Mike Tanner, director of vehicle technology and innovation at Auto Care Association, said CARB had the "impetus to create a standard" so that each vehicle had a port to get "inspected and tested to make sure it's complying with emissions" regulations in California.

In 1990, California required that vehicles sold in the state starting with the 1996 model year have onboard diagnostic systems that met the new standard.

That new standard, later known as onboard diagnostic system II, was developed by the Society of Automotive Engineers and included standard diagnostic connectors, test signals and diagnostic trouble codes.

For 1996 model year vehicles and newer, the government also mandated onboard diagnostics II in all cars manufactured in the U.S.

That CARB is the source of the standard has created some quirks in the use of onboard diagnostics for combustion engine vehicles. While onboard diagnostics is used for monitoring emissions, service shops also use the port to access information about vehicle operations for repair.

But because of the technology's regulatory history, the codes and scanning tools are standard only for emissions-related information. For other types of diagnostics, the "garage has to pay for access to get that information from the vehicle manufacturers, even if they will sell it to them or license it to them," said Tanner.

"It's expensive for a shop to pay that," he said. "It could be $50,000" plus more for an automaker-specific diagnostic tool.

There are also technical challenges created by the onboard diagnostic port. Tanner said the system has not kept pace with in-vehicle networks. The system can "very easily" get overwhelmed and prevent the transfer of information, which would be less likely if diagnostic information were transmitted wirelessly or via ethernet.

But with wireless transmission, automakers can opt to provide only the required emissions data through the port and restrict access of diagnostic and service data through telematics, meaning aftermarket parts and repair shops have access to less information than dealerships.

There's industry chatter about replacing the onboard diagnostic system II with a network using ethernet, which would allow for the transfer of greater volumes of information, said Tanner. But so far, the onboard diagnostic system II remains the industry standard.