As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT COMPLAINED OF LANDING GEAR NOT RETRACTING. FOUND HYDRAULIC 'UP' PRESSURE SWITCH TO HAVE 165 OHMS RESISTANCE WHICH IS PREVENTING A GOOD GROUND FOR THE PUMP. REPLACED SWITCH. OPS CHECK OK. SWITCH WAS REPLACED 78.2 HOURS PREVIOUSLY AS PART OF PIPER SB 964A.