99 Blazer with 4.3 and 135k miles. My "Service 4wd" light comes on after it's been running a while, mostly seem to notice it after some highway driving for 10-15 miles or so and it just pops on. Been runnign in 2w-hi the entire time, not used 4hi or 4lo in months.

Doesn't do it every time, and seems to go out after stopping at a store and coming back out and starting again after about 1/2 hour.

I've never had a chevy truck with this idot light, exactly what does this mean, the manual just says "have it serviced", but does it mean it's low on fluid in the t-case, the rear diffy need service, what ist it?

B

 

It means that your transfer case control module (TCCM) has detected a problem with the system. It could be anything from a bad TCCM to wiring or just a speed sensor. You need to have the codes read by a full feature scan tool capable of accessing the TCCM.

 

thanks for the reply.

is there a common problem area to start?

Also, I've been thinking about purchasing a scan tool, any recommendations that also read out the TCCM issues?

Thanks

 

Both topics are covered in great detail elsewhere on the forum.

For the transfer case issue, checking the THIS POST in the Tech Article (DIY) section.

On the scan tool, just remember that you get what you pay for. Quite a few people have gone for the open platform scan tools only to find out that not everything is properly defined or accessible. I have an Autoenginuity scantool and could not be happier.