My 4 wheel drive was not engaging, 4 wheel light just blinks. We replaced the speed sensor and the 4 wheel worked once. Attempted to use it again, would not engage. We unplugged battery to reset computer, 4 wheel drive then worked again once. We played around with it and discovered that when the key is turned on and just before you turnover the engine, 4 wheel will engage, and you can turn it off while truck is running. But cannot engage 4 wheel while truck is running. ABS and traction control lights are on, traction control will not turn off.

thoughts/ suggestions?

 

You have a bad sensor for the ABS

 

We changed the wheel bearing and that came with a new one, should I start with changing the sensor on the opposite side?

 

Have the codes read and it should lead you to the bad sensor, before you start throwing parts at it. From what I understand if the ABS light is on the truck won't allow you to engage 4wd. I could be wrong though.