As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING FUEL CROSSFEED AT FL350, THE CROSSFEED VALVE WAS OPENED AND LEFT TANK PUMPS WERE MOVED TO THE OFF POSITION. FORWARD PUMP LOW PRESSURE LIGHT ILLUMINATED CORRECTLY, BUT AFT PUMP LOW PRESSURE LIGHT DID NOT ILLUMINATE, NOR DID THE MASTER CAUTION LIGHT. REMOVED AND REPLACED LEFT AFT FUEL BOOST PUMP PRESSURE SWITCH. PER AMM 28-42-11.