NHTSA Complaint #11657669 — 2008 GMC YUKON

I purchased a MagnaFlow aftermarket catalytic converter system for my 2008 GMC Yukon SLT 5.3L through Walmart’s online marketplace, sold by a third-party vendor called OurDealsRock. The product was advertised as “50-state legal” and compatible with vehicles registered in New York State. However, shortly after installation, my check engine light turned on, and diagnostic codes P0420 and P0430 (Catalyst System Efficiency Below Threshold) appeared. Initially, I thought this was a minor sensor issue, but over time, the vehicle’s performance gradually deteriorated. I noticed reduced acceleration, poor fuel economy, and eventually significant loss of power. The vehicle began shaking under load, misfiring, and overheating. These symptoms worsened steadily—not immediately—but progressively after continued driving with the aftermarket converter installed. I had the vehicle inspected by a certified mechanic, who confirmed that the MagnaFlow converter was not CARB-compliant, was not approved for use in New York, and that it had been illegally marketed as such. He also informed me that prolonged use of a non-compliant, malfunctioning converter caused excessive backpressure, leading to complete engine failure over time. The diagnosis was confirmed by a second mechanic before I committed to the engine replacement. The product was later removed from Walmart’s site, becoming unavailable for sale in my zip code [XXX] ) shortly after my initial complaint. This shows clear acknowledgment that it should never have been sold to a New York consumer in the first place. But by the time it was taken down, the damage had already been done. Component/system that failed: •MagnaFlow aftermarket catalytic converter system •Ultimately caused failure of the vehicle’s engine block Safety concerns: •My family and I were unknowingly driving with a damaged and failing engine •The vehicle’s degraded performance, overheating, and power loss could have compromised our safety during highway d INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORM