From my emergency checklist (thanks 25th VFS) :
NAV. There are multiple reasons this light may illuminate and most of them involve EGI state. Possible reasons for this caution and corrective actions include:
EGI flight instrument failure
1. Set the Navigation Mode Select Panel to HARS from EGI
2. Verify an EGI FLY INST FAIL message on the CDU
3. From the RESET page of the CDU, select the EGI line select key
EGI is not ready failure
1. Verify EGI switch is set to ON on the AAP
2. Set the EGI switch to OFF for at least 10 seconds
3. Reset the EGI switch back to ON
EGI GPS failure
1. On the CDU, verify a GPS FAIL message
2. On the Navigation Mode Select Panel, ensure EGI is selected
3. From the CDU RESET page, press the REINT INS line select key, if failure persists…
4. On the Navigation Mode Select Panel, select HARS
5. On the CDU REINT page, press the REINT GPS line select key
EGI INS failure
1. On the CDU, verify an INS FAIL message
2. On the Navigation Mode Select Panel, ensure EGI is selected
3. From the CDU RESET page, press the EGI line select key, if failure persists…
4. On the Navigation Mode Select Panel, select HARS
5. On the CDU REINT page, press the REINT GPS line select key
Hope that helps.
http://en.wiki.eagle.ru/w/images/2/2e/25th_VFS_Checklists_Emergency_Procedures.pdf