As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING GROUND RUN UP OUTPUT OF ENGINE DRIVEN DRY AIR PUMP FAILED TO PUT OUT PROPER PRESSURE AT IDLE RPM. RAN AIRCRAFT UP AND AIR PRESSURE STILL LOW AT HIGHER RPM. TESTED SYSTEM AND FOUND ENGINE DRIVEN AIR PUMP NO WORKING PROPERLY. BELIEVE DRY AIR PUMP VANES ARE WORN. NO RECOMMENDATIONS.