In 2026, EVs will have an industry standard diagnostic system

Jon Lawrence's 50-year loyalty to General Motors products is being severely tested by the Chevrolet Bolt he bought new in 2019.

Now on its third battery pack, Lawrence's electric hatchback has "bricked" — died on him — twice since he purchased it. Both times, the retired executive had the car flat-bedded to the dealership from his suburban Detroit garage.

Two other times, the Bolt went into "limp mode." Each time, the dealership got it rebooted, but couldn't find the problem. The service manager told Lawrence that whatever was causing the Bolt to brick was likely something he was doing, possibly something involving the charger.

"They don't have the capability to diagnose the car … and tell the consumer or service technician, 'Here's what's wrong,' " Lawrence said. "Wouldn't you expect that the 21st century of transportation would be more technically savvy than the one of 20 years ago?"

Lawrence's Bolt — like all electric vehicles — lacks an industry standard onboard diagnostic system. While EVs do have some diagnostic capabilities, they all work differently.

Now, starting with 2026 model vehicles, all that changes. California regulations, part of the state's Advanced Clean Cars II program, require automakers to phase in a standard EV diagnostic system similar to the onboard diagnostic system II found in combustion engine vehicles.

California could become the industry standard for EV diagnostics. Seven of the 17 states that follow its emissions rules have already adopted Advanced Clean Cars II regulations. Onboard diagnostic regulations for EVs will govern plug-in hybrid and fuel cell vehicles as well.

Lawrence's difficult-to-fix EV is not uncommon. According to the 2023 J.D. Power U.S. Customer Service Index Study, the growing volume of EVs led to the first decline in dealership service satisfaction in 28 years.

Creating an onboard diagnostic system for EVs is a complex task.

The template for most of the components that will fall under the standardized EV diagnostic system can be found in California's Advanced Clean Cars II legislation and SAE International document J1979-3.

The mandate covers every part of an EV's propulsion system, battery pack, power electronics, charging system and thermal systems.

"There are a lot more inputs and outputs, especially as battery packs grow," said Rob Weiss, who chairs the SAE committee that helped create the template for the components that will be monitored via onboard diagnostics in EVs.

The clean cars rule requires battery data to be displayed on a menu in the vehicle. "You don't need a scan tool to see the basic health of the battery," Weiss said, which is "what most people are worried about."

Automakers are assessing the engineering and software resources that will be needed to comply with coming onboard diagnostic regulations for EVs.

"We've just started to digest all the specifications," said Micky Bly, Stellantis' head of global powertrain. "It's too early to determine how difficult a task it will be to incorporate OBD into EVs."

Bly said Stellantis does have "vast experience" solving onboard diagnostic problems.

"I have not heard of anything yet that is like 'unobtainium' creation — to Mars and back type stuff," he said. "We'll negotiate with some of those final standards."

GM in a statement said it is "approaching EV diagnostics the same way we approach diagnostics" for combustion engine vehicles. "We want to provide a common experience across vehicle types and service communication tools and make it easy for customers to understand potential issues and resolve them at both GM dealers and independent repair facilities."

Creating an onboard diagnostic system for EVs could be even tougher for startup automakers that don't have deep pockets and corps of experienced engineers.

"You have different challenges if you are new," Weiss said. "Startups have the challenge of learning about the OBD world in general."

Tim Reeser, CEO of Lightning eMotors, a Loveland, Colo., company that installs electric powertrains in GM and Ford commercial vehicles and is developing a chassis cab and passenger van, is following onboard diagnostic developments for EVs closely.

"One of the challenges is what are the standards going to be?" Reeser said. "It's my understanding that some parts of the system are not well defined yet."

Each EV maker using a different diagnostic system creates a bit of a "wild, wild West" situation, said Krissy Hertz, director of market development at Motor Diagnostic Systems of Loveland, Colo., which manufactures testing equipment. "Automakers are not all on the same page in terms of what kinds of tests to run. The industry needs a standard set of tests."

Hard-to-detect powertrain problems were once common among gasoline- and diesel-powered vehicles.

But thanks to the onboard diagnostic system II required in all passenger and commercial vehicles running on internal combustion, intermittent electrical or mechanical problems that leave no trace are scarce. Onboard diagnostics II helps technicians fix most combustion engine vehicles quickly regardless of whether a dealership or an independent repair shop does the work.

The system relies on parameter IDs that monitor each component spelled out in the regulations. When a part of the engine or the emissions system malfunctions or performs outside the parameters, a specific diagnostic trouble code logs in the vehicle's computer. That triggers a "check engine" or "service soon" alert in the vehicle's instrument cluster. A technician can then either use Wi-Fi or plug a scanner into the lower portion of the dash to check the parameter IDs to see which component or system triggered the alert. All combustion engine vehicles use an industry standard data port and the same coding format. The same scanner and codes work in vehicles as different in cost and performance as a Rolls-Royce Ghost and a Kia Seltos.

Some EVs on the road already use the same diagnostic port as the onboard diagnostic system II for internal combustion engine cars. And newer automakers, such as Rivian and Lucid, have some of the 2026 EV diagnostic system technology in place.

"Rivian strongly supports CARB, ACC II and the ongoing efforts to expand OBD standardization to EVs — and we're working to ensure we meet these standards as part of our vision to facilitate right-to-repair," Rivian said in an email. "Ultimately, our goal is to leverage our connected car technology, to provide advanced, secure diagnostics to third-party technicians to efficiently identify and address malfunctions."

Since 1996, as the addition of turbochargers, direct injection, advanced fuel tank venting and other technologies has brought greater complexity to vehicles, the number of component monitoring codes has grown to 196 for those powered by gasoline and diesel.

EV makers need a similar standard to detect faults and give independent repair shops "any shot at repairing some of these systems," said Matt Shepanek, vice president of testing programs for the National Institute for Automotive Service Excellence.

For Lawrence, a uniform diagnostic system for EVs can't come soon enough.

His 2012 Cadillac SRX gets repaired quickly because of the industry standard for diagnostics for gasoline-powered vehicles. He's unsure if he would buy another EV as a primary vehicle as he's lost confidence in his Bolt and filed a complaint with the Michigan attorney general's office. He worries the car will die in fast-moving traffic and leave him and his wife in a dangerous situation.

"I haven't had 100 percent functionality for all but about two weeks since I've owned the car," Lawrence said. "Even now, there's a recall dealing with problems with the charging cable. The dealer is absolutely clueless on the cause of our issues."