As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DESCENT PASSING THROUGH FL200 LEFT AFT FUEL PUMP LOW PRESSURE LIGHT ILLUMINATED CONTINUOUSLY. LEFT MAIN TANK CONTAINED APPROX 4.9K LBS OF FUEL. GROUNDED - YES. REMOVED AND REPLACED LEFT AFT FUEL PUMP, OPS CHECK GOOD IAW B737-800 AMM 28-22-41.