B737-500 FLT CREW HAS A GPWS 'TOO LOW GEAR;' 'TOO LOW TERRAIN' DURING APCH TO RWY 9R ORD.

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APCH TO RWY 9R NORMAL. WX ABOUT 5 MI OVCST; 3 SM IN -RAIN TO RAIN. AIRPLANE CONFIGURED NORMALLY WITH A FLAPS 30 DEG LNDG PLANNED. AT ABOUT 200 FT AGL WE GOT MULTIPLE EGPWS WARNINGS. I BELIEVE WE GOT 'TOO LOW TERRAIN' AND 'TOO LOW GEAR.' GEAR WAS CONFIRMED DOWN AND LOCKED PER SOP EARLIER IN THE APCH. WE THEN EXECUTED A GAR AND FOLLOWED TWR AND APCH INSTRUCTIONS TO THE SW AT AN ALT OF 4000 FT. WE WERE IMC IN RAIN DURING THE ENTIRE EVENT. ONCE LEVEL AT 4000 FT; I CONTINUED FLYING THE ACFT ON AUTOPLT AND TOOK OVER THE RADIOS. OUR FUEL STATE AT THIS TIME WAS JUST UNDER 5.0. I THEN DIRECTED THE FO TO CONTACT MAINT VIA OUR DISPATCHER USING THE LCL ORD VHF DISPATCH FREQ. MAINT SUGGESTED THAT WE CHK THAT 1 CIRCUIT BREAKER WAS SET (I BELIEVE THE GND-AIR SENSING CIRCUIT BREAKER BEHIND THE FO'S SEAT). WE ALSO DISCUSSED WITH HIM THAT WE BELIEVED IT WAS DEFINITELY AN ELECTRICAL PROB WITH THE EGPWS BECAUSE THE 3 GREEN GEAR LIGHTS WERE ALWAYS ON. WE ALSO PASSED ON TO HIM THAT WHEN WE WERE GETTING THE EGPWS WARNINGS; WE ALSO HAD THE 3 RED GEAR LIGHTS ILLUMINATED. MY FO LOOKED UP IN THE FLT MANUAL AND MAINT VERIFIED THAT 3 GREEN GEAR LIGHTS IS A CONFIRMATION THAT THE GEAR WAS DOWN AND LOCKED. I THEN ASKED APCH FOR VECTORS BACK TO ORD. WE WERE ABOUT 25 MI OUT AT THIS TIME FOR RWY 4R. WE THEN DISCUSSED WHAT MAINT TOLD MY FO AND OUR REVIEW OF THE FLT MANUAL. WE WERE 100% SURE THAT WE HAD AN EGPWS PROB UNRELATED TO THE ACTUAL GEAR POS. AT THIS TIME THE FO QUICKLY CHKED THE NOSE GEAR VIEWER PORT AND IT ALSO INDICATED DOWN AND LOCKED. WHEN THE GEAR WAS EXTENDED THIS SECOND TIME; ALL THE GREEN LIGHTS AND ALL THE RED LIGHTS WERE ILLUMINATED. WE BRIEFED TO EXPECT THE EGPWS WARNINGS ONE MORE TIME ON THIS APCH. AS WE GOT BELOW APPROX 1000 FT; WE STARTED GETTING THE 'TOO LOW TERRAIN' WARNINGS AGAIN. AT ABOUT 200 FT THE WARNINGS WENT AWAY AND THE 3 RED GEAR LIGHTS ALSO WENT OUT. WE LANDED NORMALLY ON RWY 4R AT ORD AND TAXIED NORMALLY TO THE GATE. MAINT PUT THE EGPWS WRITE-UP IN THE COMPUTER AND WE FOLLOWED UP WITH A PHONE CALL TO ENSURE THEY HAD ALL THE INFO. WE DID NOT DECLARE AN EMER OR DO A CABIN PREPARATION. THE FLT ATTENDANTS WERE ADVISED OF THE PROB AND TO EXPECT A NORMAL LNDG.