On July 1, 2026, the EPA issued guidance reaffirming something that was already law — but that manufacturers have quietly ignored for years: under the Clean Air Act, they are required to give independent repair shops and equipment owners the same diagnostic tools, service information, and training materials they provide to their own branded dealerships.
That includes DEF systems, SCR systems, DPF systems, and every other emissions control component on your truck.
The guidance came just two days after President Trump issued a June 29, 2026 Presidential Memorandum directing the EPA to act within 30 days. The agency moved fast. Whether enforcement follows is the real question.
What the Guidance Actually Says
The EPA's guidance covers on-highway vehicles and light-, medium-, and heavy-duty equipment. The core message is straightforward: manufacturers cannot gatekeep repair information to protect their dealer service networks.
According to the EPA, manufacturers must share — on reasonable terms — the service information, diagnostic software, and training resources that independent shops need to diagnose and fix emissions control systems. This is not new law. The Clean Air Act already required it. The EPA is clarifying that it intends to enforce it.
The guidance also addresses a practical repair headache: temporary overrides of emissions control systems are permitted under the Clean Air Act when the override is being done for the purpose of repair or diagnosis. That's significant for shops that need to run diagnostics without triggering fault codes or derate conditions mid-repair.
Why This Matters to You Right Now
If you've dealt with a DEF fault, a failed NOx sensor, or an SCR efficiency code, you already know the drill. The nearest dealer with the right software might be 200 miles away. You're looking at a tow bill, a multi-day wait, and a repair invoice that includes a healthy markup for the dealer's proprietary diagnostic access.
That model has been propped up largely by manufacturers restricting access to repair data — which, according to the EPA, was never legally their right to do under the Clean Air Act.
EPA Administrator Lee Zeldin framed the guidance around reducing burdens on truckers, farmers, and diesel equipment operators who depend on keeping their equipment running without being forced into manufacturer-authorized service centers.
For owner-operators and small fleets, the math is simple: more shops that can legally and technically service your emissions systems means more competition, shorter wait times, and lower repair costs.
What Independent Shops Can Do With This
If you have a relationship with an independent diesel shop, share this with them. This guidance gives them legal standing to demand manufacturer repair information and diagnostic tools on reasonable terms. If a manufacturer stonewalls them, that's now a Clean Air Act compliance issue — not just a business dispute.
The guidance covers the full stack: service manuals, technical service bulletins, diagnostic software, and training programs. Independent shops should be documenting any manufacturer refusals to provide this information, because enforcement actions typically start with a paper trail.
The Practical Takeaway
This guidance doesn't fix your DEF system today, and it doesn't guarantee your local independent shop will have OEM-level diagnostic capability by next week. But it shifts the legal ground under your feet. Manufacturers now have explicit, public EPA guidance on the record that their current gatekeeping practices may violate the Clean Air Act. That matters for enforcement, for litigation, and for the negotiating position of every independent shop trying to get access to the tools they need. Watch for manufacturer responses over the next 60–90 days — and ask your preferred independent shop whether they've been able to access the diagnostic data they need for emissions work.