What was found
PTU CONTROL FAIL ADVISORY LIGHT ILLUMINATED AFTER TAKEOFF, EVERYTHING FUNCTIONED NORMALLY. RETURNED TO FIELD. LANDING UNEVENTFUL. AIRCRAFT REMOVED FROM SERVICE. COMPLIED WITH OPERATIONAL TEST OF PTU IAW AMM 29-11-61-710-801, COMPLIED WITH F/C IAW AMM 29-11-61-720-801, NO DEFECTS WERE NOTED. NO HISTORY 90 DAYS. COMPLIED WITH VISUAL INSPECTION OF PTU COMPONENTS, AND WIRING, FOUND BACKSHELL LOOSE ON PTU PRESSURE SWITCH. SECURED THE CONNECTOR BACKSHELL AND REPLACED PTU PRESSURE SWITCH IAW AMM 29-30-11-000-801. OPS AND TESTED. LEAK CHECKED. SYSTEM OPS CHECKED GOOD. RETURNED TO SERVICE.