Service 4WD light on 1999 Silverado

I have a 1999 Chevy Sliverado 4WD pickup with 75k miles on it. On Sunday I was driving around on vacation in Nashville, TN and the "Service 4WD" light came on. I was not in 4WD and didn't notice anything unusual while driving it. I drove about another mile and shut it off. I looked for oil leaks and didn't find any. I restarted it and the light did not come on, but after driving about 2 more miles it came back on. I drove a couple more miles and shut it off. I restarted it and the light did not come on and has not come on again since after driving about another 300 miles. Any ideas about what's going on? The manual just says it means the 4WD may need service. I had it in 4WD about 10 days ago to go across a muddy field and it worked perfect then.

Assuming you have the push button 4x4 selector, it just may be a loose connection in the dash. Check to see if all the little yellow indicator lights are lit, or if while you're driving, it dims or goes off and on. Also while driving check to see if by pushing the plastic faceplate around the switches the 2wd light flickers or goes out. I had this same problem on my Silverado. The complete dash faceplate just pulls off and two small screws hold the 4x4 switches in.

Danny, I did a search on the Internet and found the following'

When SERVICE 4WD appears on your Message Center it indicates that there is a problem with your Automatic Transfer Case. The system is designed to catch many problems before they become catastrophic. When SERVICE 4WD appears you should contact your local Chevrolet dealer immediately.

You can find more information in your Owner's Manual on page 2-121.

Thanks Mike. I found that in the manual too. I'm trying to avoid going to the dealer and paying a lot of money for them to tell me it's just a bad connection somewhere or something, so I thought I'd ask here and see if anyone has had this light come on or not. If the light came on and stayed on, I wouldn't hesitate to take it in for service.

Did you also find the place that mentioned a service bulletin about this? It wont cost you anything to call a dealer and ask about it. If it really is a problem, the longer you drive with such a condition, odds are the more expensive the repair will be.

From the 2002 Chevy Avalanche Owner's Manual;

"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..."

<font color="blue">The manual just says it means the 4WD may need service.</font color>
Not to pick nits, but if your manual is the same it indicates there may be a problem, however service is required.

Just trying to avoid you getting into another situation you'll regret (7308 vs BH FEL), i.e., "Why didn't I take the truck in when the light came on?"

Danny,

Could be one of 3 things:

1. Bad switch as mentioned
2. Actuator
3. Actuator Module

I have a 2003 and the message came on before 500 miles. The dealer's first attempt was to flash the computer, this fix lasted about 50 miles. Mine turned out to be the actuator. The dealer mentioned that this is a common problem and usually flashing the computer fixes the problem

Mike, No I didn't see the service bulletin. Where is that? I guess I'll call the dealer and ask. Thanks!

gobbler - What does it mean to "flash the computer"? Is that reprogramming it? What is the "Actuator"? I'm guessing it's the shifter that engages 4WD? What is the "Actuator Module"? Thanks!

<font color="blue"> Mike, No I didn't see the service bulletin. Where is that? </font color>
Danny, can't remember. I did a Google search on 'Service 4wd' and one of the hits was one of those sites that mentions the title of the Service Bulletin, but requires you to subscribe to see the content.

<font color="blue">...requires you to subscribe to see the content...</font color>

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