So if you've checked fuses
#72 and
#73 in the Fuse and Fusible Link Block and fuse
#58 in the IPDM E/R and they are ok. You've replaced the Daytime Running Light Relay. That still leaves some things to be sorted out:
Check DRL relay power supply - Remove DRL relay and check the voltage between the DRL harness connector (E104) and ground. Terminals 2, 5, and 7 should show battery voltage when checked against ground. If not, repair or replace harness.
Check DRL circuit - With the DRLs energized, check the voltage between the IPDM E/R harness connector (E126) and ground. Terminal 85 should show 0-1 VDC when the DRLs are on and 9-16 VDC when off. If the voltage is fixed at 9-16 VDC regardless of the DRL being on, then you may be looking at replacing the IPDM E/R or the BCM.
If the voltage is fixed at 0-1 VDC, then the DRL relay control signal circuit needs to be checked by removing the DRL relay, disconnecting the IPDM E/R harness connector and checking the continuity between the IPDM E/R harness connector (E126/terminal 85) and the DRL relay connector (E104/terminal 1). If continuity exists, then the IPDM E/R needs to be replaced or if not, repair or replace the harness.
Check DRL ground circuit - Check the continuity between the front combination lamp harnesses and ground. Connector E42/terminal 4 for the RH front combination lamp and Connector E41/terminal 4 for the LH front combination lamp. If continuity exists, then it could be the front combination lamp. If continuity doesn't exist then the harness needs to be repaired or replaced.
I think you've done the obvious by checking the fuses and replacing the DRL relay but to do these other tests properly requires a CONSULT scan tool so you may want to consider having your Infiniti service department troubleshoot your DRL system, IMHO.
