Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human-Machine Interface
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew FLC complied w / Automation / Advisory
Human Factors
I was the pilot flying on the leg into ZZZ. We were set up for the RNP M RWY XX. I made 2;000 at ZZZZZ a hard altitude instead of an at or above to make sure I wasn't high on my arrival. After being cleared for the RNP M to Runway XX in ZZZ; I was in LNAV and VNAV and in the path so I set field elevation. Prior to reaching the XXX fix; we were told by ZZZ Center of a low alt alert. We were at 4;200 and the min alt prior to XXX fix is 5;000. We were in VMC with all terrain in sight. We climbed back up to 5;000 and continued with the approach and landed uneventfully on XX. Somehow the 5;000 restriction got removed from the XXX waypoint in the legs page of the FMC; so we descended through it while established on the VNAV path.Pilots need to be careful to check all altitudes on the legs page to prevent this from occurring.
B737 First Officer reported receiving a low altitude alert from ATC while on an RNP approach after entering the airport elevation in the FMC; which may have removed an altitude restriction.