NHTSA complaint #521488 (ODI reference 10110377) concerns a 2001 GMC SIERRA and was filed on February 11, 2005. The owner reports the failure occurred on February 9, 2005. The report was geocoded to Texas based on the filer's self-reported location. The affected component is categorized as service brakes, hydraulic:foundation components:differential proportional valve, one of NHTSA's standardized taxonomy codes used to group defect patterns across make, model, and year.

The filer flagged the following severity indicators: crash: no, fire: no, injuries: 0, fatalities: 0. No crash, fire, or fatality was associated with this report, which places it in the early-warning stream rather than the priority-review stream. Because a VIN was supplied, this complaint is tied to a specific vehicle and not just a model-year cohort.

Individual complaints are consumer-submitted and unverified by NHTSA engineers — the agency's role at this stage is to collect, index, and make them searchable. What matters for federal action is the pattern: when many owners of the same GMC SIERRA cohort independently describe similar service brakes, hydraulic:foundation components:differential proportional valve failures, defect investigators have grounds to open a PE and request manufacturer data. Related filings for the same vehicle and component appear below, and the detail page for the full 2001 GMC SIERRA shows the complete component-level complaint distribution alongside any active investigations or recalls.