4x4 switch is a no go

[419TrailWisperer]

Went to a hockey game tonight. Everything was fine when I got there and when I came back out to my truck... "Service 4x4 Drive" light on dash, no lights on my 4x4 switch, and no response from the electric motors. 4 wheel drive was working fine last time I used it, about 2 weeks ago. Im thinking the 4x4 switch is going bad, but honestly I have no idea. what do you guys think? Im assuming I cant use the flow chart, given I cannot confirm 4x4 is engaging. Please, feed me your wisdom

[TBYODA]

Have you tried with truck off to go from 2HI <-> 4wLo a bunch of times?

[Trail X]

Mike, its definitely an electrical problem. Either your switch or your transfer case control module. The Roadie knows a lot more about this side of the equation. I'd say - wait for him to show up, but in reality, you may need to PM him and direct him to this thread. He hasn't been around much lately.

[DirtyBacon04]

if you're not getting any lights on the switch, then I suspect the switch itself is your culprit. If there was a fault in the actuator or xfer case, you'd just get flashing lights on the 4Auto, 4hi, and 4lo (whichever is selected)

flip the switch a whole bunch to clean contacts, but I doubt that's the issue. my guess is your switch is either FUBAR or unplugged.

Again, Roadie is your expert to reference.

[rScherzer]

I just looked at a few the the TSB's for the 03 TB, there are a few things that they have, One is checking the large connector next to the fuse block under the hood. GM says it may have the harnness pulled to tight or connector problmes within. The fix for this would be to relocate the connector. If their is terminal problems within the connector they would need to be repaired or replace. (spread terminals or corroded) I also put dielectric grease on all the terminals to help insure a better connection. Some of the other things to check is the voltage to the 4wd system. The 4wd fuse in the fuse block under the rear seat, (fuse #48 15amp) is controlled by the ignition switch. It is posible that the switch has internal resistance and is causing a low voltage to that part of the circuit. to test that you would need a volt meter taged into that circuit and cycle the key on and off checking the volage every time. (should be about the same as batter voltage) I also seen a few programming updates for the transfercase control module but that is going to require you t vist a dealer. If the service 4wd light hase since gone off, and your 4wd system is working normaly, then the problem is going to be hard to find as it is intermittant.