My 99 jimmy has a issue with 4by4. It will go in 4lo from neutral but will not shift out of first. 4hi it may be going into. All wheels are in gaged but sounds like 4loand it won't shift past first also. And 4hi won't work while trying to engage moving. And when I put in either they both stay lit up. Disconnected battery other day and fuse and tried it then and 2w and 4w stayed lit up once in gaged. And now it's back to how it was before. Lease help anyone

 

I have never heard of the transmission being limited by the setting of the transfer case or front axle.

Do you have the 3-button or 4-button 4wd system?

 

I think a bad speed sensor can cause that. There are a couple of them, but I think it's the one on the transmission. The problem is that the PCM only "sees" the speed at the driveshaft, and doesn't upshift because it doesn't "think" you're going fast enough. A decent scanner should be able to check the output from both sensors.