What was found
WEATHER RADAR AUTO MODE SHOWS LARGE WEATHER RETURNS THAT DONT EXIST. MANUAL MODE APPEARS TO WORK CORRECTLY. GROUNDED-YES. PERFORMED B737-800 FIM 34-43 TASK 801 AND TASK 814. PERFORMED WXR SYSTEM OPERATIONAL TEST, REF B737-900 AMM 34-43-00-710-802-001. COULD NOT DUPLICATE REPORTED FAULT IN ANY TESTS, WXR SYSTEM DISPLAYS NO FAULTS. WXR OPERATIONS CHECKS GOOD, ETOPS GROUND VERIFICATION SUCCESSFUL.