Service 4WD Message Light

[dmarty]

I have a 1999 Silverado LT 5.3, auto-4WD with 271k miles. I've searched other threads on this problem and the answer is not clear. The "Sevice 4WD" messeage light comes on every few days. It always comes on in 2WD when driving on the highway at 55 to 65 mph. When I stop, the 4WD seems to work normally (although it's hard to tell on dry pavement in the summer, but there appears to be plenty of driveline windup) and the next time I start the engine and drive it, the mesage light is not on and will stay off for a few days to a week. I have not used 4WD since last winter. I had a similar problem at 112k miles when the dash 4WD auto control failed. At that time, the dash control lights blinked in a goofy way and the 4WD refused to engage when I tried to use it. I replaced the dash control and everything has worked fine until now. Most of the other threads say it's the dash contol unit with one claiming it's either the front axle actuator or the transfer case actuator.

My questions are: Can the dash control fail in different ways or are the symptoms this time indicating a problem with either the front axle or transfer case actuators? Should I keep driving it until it fails completly so it's easier to find the problem? If I do, will it leave me stranded? Will an aftermarket code reader give me a more detailed code explanation or will it have to be connected to a Tech2?

Thanks,

dmarty

[Cobblemizer]

When the service 4wd light comes on check to see if the 2wd light is lit, my 04 had the service light come on and the dealer told me its because the light in the switch is going bad and you have to replace the whole switch.

[dmarty]

Thanks. Don't remembr if the 2WD light was on or not. I think it was , but not sure. I'll look next time.

[dmarty]

Message light came on again today. Same thing, higway speed everything normal except message light. The 2WD light was on and did not change when the message light came on. When I turn off the engine, the message light goes out and stays off for a few days. Any ideas?

Thanks

[Black 95 TSI]

I have seen the 4wd switch cause this alot. HAve the computer scaned. You have to look under transfur case. i think the cose is B1629. The 4wd switches go bad alot.

[dmarty]

Thanks for the info.

[dmarty]

Replaced the dash control 3 weeks ago and the message center has not come on since. When I replaced it, I noticed the OEM name on the back of the control, Lucas!!!!! This is the only part on the truck I've had to replace more than once in 275k miles. For those of you not familiar with Lucas, they're a British company that has a terrible reputation for quality. The British car guys refer to Lucas as "Sir Lucas. Prince of Darkness". Why GM would buy parts from them is beyond me. Low bid I guess.

[bwood]

I wonder if Lucas makes the control head in my wife's malibu. Cars 11 years old 97,000 miles, on its 6th control head.

[Black 95 TSI]

I know there is an updated switch from GM. I just had to put a switch in a 3500 4x4 for keeping the front axle locked in.

[dmarty]

My parts guy is really good and he didn't say anything about an update part. I think he would have mentioned it if one was available. Maybe all of the replacement parts are the new type. Guess I can't complain. It takes all of 5minutes to change the switch and my cost on the part is $59.00. Could be worse.

[Black 95 TSI]

All the switches should be the new ones.