Follow-up to a prior complaint on this VIN regarding a dangerous limp-mode event caused by a failed DEF injection nozzle. While climbing a steep grade on XXX in [XXX], the DEF dosing nozzle leaked, putting the vehicle into limp mode. Vehicle was limited to ~27 mph while surrounding traffic, including semi-trucks, moved at ~65 mph, creating a serious collision hazard on a grade with limited passing room. An authorized MB dealer (Mercedes-Benz of [XXX], [XXX]) replaced the nozzle. Vehicle then re-entered limp mode with no codes stored. Further diagnosis found the DPF clogged/broken, requiring full replacement. Prior to this trip, the same vehicle's EGR valve had already been cleaned twice and eventually replaced with the EGR cooler. Mercedes-Benz has separately extended the EGR valve warranty on this model range to 15 yrs/150,000 miles, indicating a known reliability issue. EGR problems are mechanically linked to DPF soot loading, and may have contributed to this DPF failure. All failures (EGR, DEF nozzle, DPF) occurred at approximately 72,815 miles – well under 100,000 miles and well short of the manufacturer's stated ~150,000-mile design life for these components. Filing to document a pattern of premature emissions-system failures on this platform and the real safety hazard created when the vehicle was forced into a dangerously slow, uncontrolled speed on a high-traffic mountain highway grade. It appears both the Diesel Particulate Filter, Injector Nozzle were the main failure points of this emission system. It should have at least a 10 year, 100,000 mile warranty (not 5yr, 100,000)! VIN: [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Source: NHTSA complaint ODI #11755069 · view all complaints for this vehicle at nhtsa.gov