Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 212; Flight Crew Type 12210
Troubleshooting; Workload; Confusion; Human-Machine Interface; Situational Awareness; Time Pressure
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Ground Equipment Issue; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Provided Assistance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew FLC complied w / Automation / Advisory
Environment - Non Weather Related; Aircraft
During our descent into ELP; we noticed 'GPS L & R Invalid' messages on the FMC.  We checked the POS page of the FMC and there were no coordinates displayed in the GPS L or GPS R fields. We also noticed the transponder had a fail indication in both the 1 and 2 positions.  In addition; we had an amber TERR POS indication on both NDs and no green; amber; or red terrain information displayed.  We initially thought these indications may be associated with the frequent GPS jamming that occurs in this part of the country. Our weather packet did not contain a note of that possibility. Later; we talked to Approach Control about the GPS jamming and they told us it happens often; sometimes all night.We used the RNAV Z from WIKKR to align with Runway 22 and then transitioned to an ILS. While on final approach at approximately 500 feet AGL we received a GPWS PULLUP indication. We performed the terrain avoidance maneuver and got vectors back around to Runway 22 again. We couldn't find any guidance in the QRH for our lack of terrain information/amber 'TERR POS' on the NDs. The second ILS to 22 produced the same result with another terrain avoidance maneuver. After the second go-around; the TERR POS indication went away on both NDs and we started seeing green; amber; and red terrain information being displayed on the NDs. We got vectors back around to Runway 22 and landed uneventfully. After talking with Maintenance; we deferred the jet's GPWS.I did not perform an FMC navigation check following the initial 'GPS L & R Invalid' FMC messages. I'm not sure if that would have alleviated the situation. I was more concerned about the amber 'TERR POS' indication and lack of terrain data on the ND which I had never seen before. There is nothing in the QRH on how to deal with that indication. I can't explain why the amber 'TERR POS' indication went away and terrain information returned to the ND while being vectored for the third approach. I also don't know if GPS jamming was a factor; since our weather packet did not have a note about that possibility. I am thankful I was tankering 5500 pounds and the weather was nice.
Air Carrier Captain reported the aircraft's 'R and L GPS' system malfunctioned during 2 approaches into ELP. The terrain warning activated on each approach and no terrain was displaying on either PFD. The navigational systems returned to normal on the next approach. The Captain suspects GPS jamming.