Why would a 2000 GMC Jimmy 4x4 not engage?

Answer 1

It's electronic, check all fuses, also check the connection to the transfer case.

Try listening to the transfer case try to engage. Mine did not engage after an engine wash. The vacuum actuater on the firewall above the distributor was not allowing vacuum to the front axle actator. You can put the truck on jackstands (all 4 wheels) and check to see if the front drive shaft engages. If so, then it's probably the vacuum actuator or the axle actuator.

My 2000 GMC jimmy had 4x4 issues. Were it would intermittently work. After numerous attempts to fix it. I found out that the control module has a metal shell which create a lot of moisture and causes corrosion which lead to the heart of the problem. Here is some home made steps I took which ended up fixing the problem.

1) check that your vacume lines are not dry and brittle, if so replace...cheap fix

2) check the vacume actuator under the battery case. If free and working its OK

3) there is a sensor on the front axle that tells the TCM if it is engaged or not . Make sure it is tightened properly. Mine wasn't.

4) the TCM on the passenger side has a connector issue. With a second person switching it in and out, wiggle the connection to see if it is loose. If so zip tie it . You will hear it engage and disengage.

5)check and clean the vacume valve on the transfer case. This. Should be part of the vacume lines.