B737-700
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 140; Flight Crew Type 3031
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem
Aircraft
I was Pilot Flying. On approach to Runway XXR at ZZZ; after calling for the landing gear down and flaps 15; we noticed that we had three green and three red landing gear indications. The overhead panel showed three green indications. We were able to complete the QRH and Landing Checklist and determined that the landing gear was down and locked. We continued the approach with the intention of landing. At approximately 500 feet AGL; we received the oral warning 'TOO LOW GEAR.'I was no longer sure that the landing gear was down and locked.  I called for the go-around and executed the go-around procedure.  We decided to leave the landing gear down and cleaned the flaps up to 5 degrees.  The Captain was working the radios and informed ATC of the go-around.  ATC gave us a heading and cleared us to 2;000 feet. They asked for the reason of the go-around. The Captain informed them that we were having landing gear indication problems. The Captain then decided to request priority handling.We completed the QRH and were able to get three green indications without red indications. The Captain informed ATC we had solved the problem and could continue for another approach and landing.  ATC assigned us Runway XXL.  We set up the FMC; re-briefed the approach; completed all of the appropriate checklists; flew the approach; and landed uneventfully on Runway XXL.  We taxied to the gate; shut down the engines and completed the Shut Down Checklist. While at the gate we had realized that due to workload; we had forgotten to inform the flight attendants of the priority handling situation.To prevent this from happening again; we need to slow down; and complete all briefings to the Flight Attendants and Passenger cabin prior to landing. Just because we were able to solve the landing gear problem and workload was heavy; does not alleviate the duty to inform the Cabin Crew.
B737-700 First Officer reported a landing gear indication issue during approach resulting in a go-around.  The flight crew ran the QRH procedures; resolved the issues and landed safely on their second attempt.