4X4 Auto not working

[rsilva708]

So in the snow we got the other day, I found out that with the 4x4 selector switch in auto, I don't get the fwd when the rear tires spin. But when I select 4x4 hi or low, all 4 wheels work fine. What would cause the auto4x4 to not work?

TIA

 

[gijoecam]

Could be a bad speed sensor not detecting the slippage, or could be the TOD relay not actuating it... Without a scanner to monitor the GEM inputs and outputs and the duty cycle of the TOD relay, it's a guessing game at best...

-Joe

 

[rsilva708]

I guess I'll have to take it into a shop to get looked at.

 

[gijoecam]

I guess I'll have to take it into a shop to get looked at.

I can't tell you wahat it is without being there to poke and prod, but I can tell you that if it works in 4high and 4low, it's absolutely NOT the shift motor or the transfer case itself, but someting in the Torque On Demand control circuitry.

Good luck! Let us know what they find!

 

[ejbeach]

my 99 did it last year was a bad rear driveshaft output sensor, very easy to change, i would just change both of the sensors, the one for the front shaft is behind the shift motor, its easier to take the motor off and the 2 sensors with it cause they are wired to the same harness/connector.