Service 4wd light coming on when warmed up...
 

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. :icon_wink:

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.