The diagram I have for the fuse box is downloaded from the net, is it trustworthy? It is an GMC Envoy 2003 manual.

Question edited for clarity.
Question moved to model category.

Here are all your fuses

GMC Envoy (2002-2009) fuses and relays

https://fuse-box.info > gmc > gmc-envoy-2002-2009-f...

Here you will find fuse box diagrams of GMC Envoy 2002, 2003, 2004, 2005, 2006, 2007, 2008 and 2009, get information about the location of the fuse panels ...

Hi,

Please open your fuse box to check if you notice any fuses that are discolored or (potentially) burnt. if you find one, that fuse might be linked to the dome lights.

To be sure, please call your local advanced auto parts to verify the fuse # is correct and then you can order the fuse through advanced autoparts.

Thank you.

If possible, pull the horn relay, use jumper wire on switch side of relay, right side in diagram. If the horn sounds, it's not the fuse. Sometimes these diagrams don't post, for some reason? good luck

Page 372 or 6-57 starts the fuse box diagram in owners manual
https://my.gmc.com/content/dam/gmownercenter/gmna/dynamic/manuals/2002/gmc/envoy/2002_gmc_envoy_owners.pdf
fuse box diagram below
https://www.autogenius.info/gmc-envoy-2002-fuse-box-diagram/
https://www.youtube.com/watch?v=0LFaIfh1aoA
You may need to check all fuses below may help
If you check and only one side has power with ignition on pull the fuse and verify the fuse is blown.
https://www.youtube.com/watch?v=ksrsXwwukFc

https://www.youtube.com/watch?v=pHkgjXKdUvs

https://www.youtube.com/watch?v=pbaj0dOG2vg

there are 4 places the fuses could be. 1. under the dash next to steering column. 2. left side of dash under the cover only seen with door open. 3. right side of dash under cover only seen with door open. 4. under hood under a plastic cover probably to the right near battery.
this link says fuse 31
http://www.autogenius.info/gmc-envoy-mk2-second-generation-2003-fuse-box-diagram/

Fuse number 13 is the cigarette lighter fuse, it is in the engine compartment fuse box on your GMC Envoy. To know more about where each fuse is and what it does, follow this link: https://fuse-box.info/gmc/gmc-envoy-2002-2009-fuses-and-relay

Check your owner's manual for a fuse box diagram and check the appropriate fuses. This may also be a high amp fuse that is in the fuse box under the hood. Please rate this answer, thanks.

Check fuse --if blown -replace. Posibly wiring connector under seat unplugged.

There are two fuse boxes/block

One fuse block is located under the hood in the engine

compartment on the driver's side of the vehicle.

Remove the primary cover by pressing the two locking

tabs. Remove the secondary cover by snapping off

while lifting. To reinstall the fuse panel cover, reverse
the sequence.

The 2nd fuse box is located under the rear seat cushion

If I remember correctly if you look at the back side of the fuse cover, it should tell you what the fuses are. Also in the owners manual in the index, under fuses, it should give you a diagram of the fuse location for the acc. outlets. Good luck. The fuse should be a 20 or 25A fuse.