Preventive Maintenance Inspection (PMI)
Fundamentals
PMI is a documented, systematic inspection: walk-around, under-hood, under-vehicle, and operational checks. Know the DOT annual inspection requirement, CVSA out-of-service criteria, and the difference between a maintenance inspection and a federally required annual inspection - the annual inspection must be performed and documented by a qualified inspector. Cover fluid levels and condition, belt and hose condition, tire tread and pressure, brake adjustment, air system leaks, steering play, suspension components, lights, and safety devices.
Common specifications
- Steer tires: typically 4/32 inch minimum tread depth; other tires 2/32 inch.
- Brake pushrod stroke: must be within the chamber's stamped limit.
- Air leaks: system must hold pressure within published limits with brakes released and applied.
- Belts: cracked, glazed, or frayed belts are replaced, not adjusted.
Traps
Questions ask what makes a vehicle out of service - a cracked brake drum, a missing lug nut, an audible air leak, or a tire below minimum are all classic answers, while a dirty air filter or low washer fluid is not. Another trap confuses "recommended service interval" with "out-of-service condition."
Worked example
A driver reports a soft pedal. During the PMI, the inspector finds pushrod stroke of 2 3/8 inches on a standard-stroke chamber limited to 2 inches. That exceeds the limit, so it is a brake adjustment violation and out-of-service item, not simply a note for the next service. Document it, correct the foundation brake, and re-inspect.