Service 4WD light?

You can try to disconnect the 4 wheel drive module for 30 seconds and see if it comes back on. Sounds like the module needs to be replaced. You may have to go to a dealer and have a scan tool put on it and see if the module is getting communication.

Its behind the 4 wheel drive switch but above the drivers side fuse box. Its a 2 connector module.

I hope this gets to soon, try to disconnect the fuse for 30 seconds instead of pulling the module out. This will do the same thing.

I don't know that I can or can not help. But I don know that there is a good chance that more information is needed. Although someone may throw in a helpful post, My software needs more specifics.

What size truck K1500, K2500 etc?

What size engine 4.3, 5.3 etc?

Does the light say "4x4" or "4wd" or other?

Clarify the dash switch lights. All the lights on the dash? Or is there a light on the switch?

IT would be helpful to get the codes out of the computer for this. I don't know that this is necessarily a mechanical isue, a Instrument cluster issue or a CAN issue.

Im not 100% sure. You may wanna call a parts department and find out. What is the code that he got.

Yes, you should have it scanned for codes. Then post the codes for us please.

Your scanner might not be able to read transfer case DTCs. I use a TECH2 scanner. They run around $4,800.00

Here is a copy of a service bulletin. If your symptoms match this, follow the directions.

Subject: Service 4WD Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch) #02-04-21-004 - (04/15/2002)

Models: 1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL)

with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)

Condition
Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.

Cause
The condition may be due to a intermittent fault in the transfer case shift control switch.

Correction
Important: The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.

Replace the transfer case shift control switch using published Service Information procedures.

Parts Information
Part Number
Description

15709327
Transfer Case Shift Control Switch

Parts are currently available from GMSPO.