There are two main components for the four wheel drive. The powertrain control module (PCM) and the front drive axle actuator pump. The pump is controlled by the PCM. The pump compresses air to engage the front axle. When the transfer case is in four wheel drive (4H or 4L), the four wheel drive switch closes providing a ground signal to the PCM. The PCM actuates the pump which pressurizes the actuator in the front axle. This pressure engages the axle hub which connects the front drive shaft to the axle shafts, allowing the transmission/transfer case to turn the front wheels. The PCM will not operate the pump for more than 10 seconds in order to protect it. The PCM will also provide a path to ground for the 4WD indicator in the instrument cluster. The indicator is provided battery voltage when the ignition switch is in the ON or START position through the IG fuse. With power and ground supplied, the indicator lights.

When the transfer case is in 4L (with auto trans), the four wheel drive low switch sends a ground signal to the PCM. The PCM will not engage the torque converter clutch while this signal is being received.

When the transfer case is returned to the two wheel drive mode, the release valve in the pump opens and releases the pressure in the actuator. Without pressure, the hub disengages.The PCM also releases the ground to the 4WD indicator which causes the indicator to turn off.