California Lemon Law Lawyer: What Counts as Substantial Defect

If your car keeps going back to the shop for the same issue, you may be wondering if California’s Lemon Law applies. The key questions are whether the problem is a “substantial defect” and whether there have been enough repair attempts. Below, ZapLemon explains these core concepts in plain language so you can better understand your options and what to do next.

What Counts as a Substantial Defect in California

Under California’s Lemon Law (part of the Song-Beverly Consumer Warranty Act), the issue must be a “nonconformity” covered by the manufacturer’s warranty that substantially impairs the vehicle’s use, value, or safety. In everyday terms, that means the problem is more than an annoyance—it meaningfully affects how you drive the car, what it’s worth, or whether it’s safe. The defect also cannot be caused by abuse, neglect, or unauthorized modifications.

Safety-related defects are often the clearest examples of substantial problems: brake failures, steering issues, airbag or seatbelt malfunctions, electrical shorts that cause stalling, or fuel and oil leaks. Problems that impair use can include transmissions that slip or hesitate, engines that lose power or overheat, or electrical faults that leave the vehicle in limp mode. Defects affecting value may include persistent water leaks leading to mold, paint or body defects that recur after attempts to fix, or chronic warning lights that scare off buyers and reduce resale value.

Not every issue qualifies. A single rattle, an occasional infotainment glitch, or a one-time warning light that never returns may not rise to the level of substantial impairment. That said, seemingly “small” issues can become substantial if they persist or create safety risks—such as a backup camera failure that compromises visibility or repeated charging faults in an EV that leave you stranded. Because each situation turns on its facts, good documentation is crucial: keep repair orders, note dates and mileage, and describe symptoms consistently.

Repair Attempts and California Lemon Law Thresholds

California’s Lemon Law looks at whether the manufacturer had a “reasonable number” of opportunities to fix the problem. The law also includes a helpful presumption (often called the Tanner presumption) within the first 18 months or 18,000 miles, whichever comes first. During that period, your claim is presumed valid if: the same defect was subject to repair at least four times; or a defect likely to cause death or serious bodily injury was subject to repair at least two times; or the vehicle was out of service for repair for a total of more than 30 days.

These numbers are guidelines, not hard limits. You can still have a viable claim even if your repairs fall outside the 18-month/18,000-mile window or don’t hit those exact counts, especially if the defect is serious and ongoing. Likewise, “30 days out of service” generally refers to cumulative days the car spent at the dealer for warranty repairs, even if the days aren’t consecutive. Courtesy loaners don’t erase days your own car is in the shop.

What counts as a repair attempt? Any documented visit where the dealer had a chance to diagnose and fix the issue. A “could not duplicate” or “no problem found” entry still counts as an attempt if you reported the same symptoms. To protect yourself: schedule repairs promptly, avoid clearing trouble codes before service, describe the symptoms the same way each visit, and save every repair order, email, and text. If the problem continues, consider notifying the manufacturer in writing and consult a California Lemon Law lawyer to review your timeline and paperwork.