Check 4 WD

[doctorhrdware]

My wife has a 2000 z71 5.3L. It will intermittently get a chk 4 WD, yellow light. There is no consistency to when the light will come on, temperature has no effect as to when the light will come on also. I am not sure where to start to trouble shoot this problem. Any help will be greatly appreciated.

[HC2000]

Hi,
I have a 99' GMC Z71 and the owners manual reads as follows:

"If the SERVICE 4WD message comes on, there may be a problem with the Automatic Transfer Case and service is required. Malfunctions can be indicated by the system before any problem is apparent, which may prevent serious damage to the vehicle. The system is designed to assist your technician in correctly diagnosing a malfunction."

I would first check the fluid levels in the transfer case and front differential. If that light persists you probably should get it checked. Good luck.

[OGG]

90% of the time it's the switch on the dashboard. I had the same problem. I changed the switch, problem solved. The switches are all really crappily made in Mexico so they fail often. So far I've replaced 4x4 switch, power lock mechanism, power mirror switch and I think my heater switches are getting flaky. By contrast in all of my previous vehicles I think I've replaced 1 power window switch.

[weo38]

My light went on and it was because the software in the computer needed to be updated. But I would definitely take it in and have it looked at. Mine came on with no rhyme or reason either. It was $100 to get the update btw.