FOUR LOW MODE INDICATOR

The four low mode indicator gives an indication to the vehicle operator that a LOW range operating mode of the four-wheel drive transfer case is selected. On vehicles equipped with the Command-Trac four-wheel drive system, the four low mode indicator lights when the transfer case is engaged in the 4L (Four-Wheel Drive Low Range) position. On vehicles equipped with the Selec-Trac four-wheel drive system, the four low mode indicator lights when the transfer case is engaged in the 4 LO (Four-Wheel Drive Low Range) position.

This indicator is controlled by a transistor on the instrument cluster circuit board based upon the cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The instrument cluster must be electronically configured for the type of transfer case in the vehicle using a diagnostic scan tool in order to provide proper operation of the four low mode indicator.

The four low mode indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be OFF when the ignition switch is in any position except ON or START. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the four low mode indicator for the following reasons:

  • Four Low Mode Indicator Lamp-On Message - Each time the cluster receives an electronic four low mode indicator lamp-ON message from the PCM indicating that a low range position of the four-wheel drive transfer case has been selected, the four low mode indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the PCM or until the ignition switch is turned to the OFF position, whichever occurs first.
  • Actuator Test - Each time the cluster is put through the actuator test, the four low mode indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.

The PCM continually monitors the transfer case switch to determine the driveline operating mode. The PCM then sends the proper lamp-ON or lamp-OFF messages to the ElectroMechanical Instrument Cluster (EMIC).

For proper diagnosis of the transfer case switch, the PCM, the EMIC, the PCI data bus or the electronic communication related to four low mode indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.