this morning wife drove for about 2 miles in 4 low not sure what speed there was alot of snow on the ground it would not go back to 2 hi thats why for some reason she went in 4 low she called me 2 mile later and told me it wont go into 2 hi and it says service rear end what all could be wrong with 2001 blazer

 

Never seen a service rear end light, Sure it don't say service 4wd?

 

I'm going with 'Service 4wd' light as well. There is no such thing as 'Service Rear End' in these trucks.

The 'Service 4wd' light means that the TCCM has experienced an error and has recorded a code describing said error. The fact that it was stuck in 4LO says that there is a problem that the TCCM has recorded and has limited shifting as a result. A high feature scan tool will be required to read the codes which is pretty much the first step if you want to solve this problem.

If you want to just try to get it back in 2HI, then you can try disconnecting the battery which will reset the TCCM and may allow for the proper transfer case shifting for a time.