EPA says manufacturers must provide info needed to repair ‘faulty DEF’ and other emissions control systems

The U.S. Environmental Protection Agency (EPA) announced new guidelines requiring manufacturers to provide owners and independent shops with the information they need to diagnose and repair emission control systems on heavy-duty vehicles.

In guidance issued on July 1, 2026, the EPA reaffirmed that “the Clean Air Act (CAA) supports Americans’ Freedom to Fix their own vehicles and equipment, regardless of vehicle or equipment type.”

“EPA’s guidance affirms that, under the CAA, manufacturers must provide Americans access to the same service and repair information they make available to their own branded service centers. This includes Diesel Exhaust Fluid (DEF) and other environmental control systems for on highway vehicles,” the agency said.

The EPA said that manufacturers must provide:

• Full emissions-related service information
• Training materials
• OBD data and enhanced diagnostics
• Passthrough reprogramming information
• Manufacturer-specific tools for purchase

“These regulatory provisions ensure that owners and independent repair shops can legally and effectively repair modern vehicles and engines,” the EPA said.

Officials said that confusion over CAA anti-tampering rules cost American truckers, farmers, and other diesel equipment operators time and money:

“For years, manufacturers have worked to provide consumers and independent repair shops with the same diagnostic and repair information they provide to franchised dealers. However, the CAA anti-tampering laws have caused some confusion regarding whether giving out certain tools and information would be considered enabling the tampering of emission control systems. This has forced Americans to travel long distances, hurting productivity, to get costly repairs done by manufacturers, when the repair easily could have been done at home or at a local repair shop. The CAA clearly states that temporary overrides of emission control systems are allowed when it is for the “purpose of repair” to that equipment to obtain proper functionality. EPA’s guidance, therefore, clarifies that light-, medium-, and heavy-duty vehicle manufacturers have a long-standing legal obligation to release the service information, training information, and tools necessary to diagnose and repair vehicles, including faulty DEF systems, on reasonable terms.”  

The guidance was issued in response to a directive in the Presidential Memorandum, “Lowering the Cost of Living by Promoting the Freedom to Fix” issued on June 29, 2026.

“Within 30 days of issuing his Presidential Memorandum, President Trump wanted EPA to act. We have operated at Trump speed and provided relief to American operators within just two days,” said EPA Administrator Lee Zeldin. “The freedom to fix allows operators to fix broken machinery easier and faster. Today’s action builds on the great work the Trump Administration has accomplished to lower costs for hard-working Americans.” 

You can learn more about the EPA’s new guidance here.