Shift Indicator - A/T: Description and Operation
SHIFT INDICATOR (TRANSFER CASE)Part Time Indicator
A part time indicator is standard equipment on all instrument clusters. The part time indicator is located near the lower edge of the tachometer dial face in the instrument cluster. The part time indicator consists of a stencil-like cutout of the words "PART TIME" in the opaque layer of the instrument cluster overlay The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. An amber Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the "PART TIME" text to appear in amber through the translucent outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board. When the exterior lighting is turned ON, the illumination intensity of the part time indicator is dimmable, which is adjusted using the panel lamps dimmer control ring on the left control stalk of the multi-function switch. The part time indicator is serviced as a unit with the instrument cluster.
The part time indicator gives an indication to the vehicle operator that a four-wheel drive part time operating mode of the transfer case is selected. On vehicles equipped with the standard Command-Trac four-wheel drive system, the part time indicator lights when the transfer case is engaged in the 4H or 4L positions. On vehicles equipped with the optional Selec-Trac four-wheel drive system, the part time indicator lights when the transfer case is engaged in the 4 X 4 Part Time position. This indicator is controlled by a transistor on the instrument cluster electronic 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 configured for the type of transfer case in the vehicle using a DRBIII scan tool in order to provide proper operation of the part time indicator. The part time 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 part time indicator for the following reasons:
- Part Time Lamp-ON Message - Each time the cluster receives a part time lamp-ON message from the PCM indicating that a four-wheel drive part time position of the transfer case has been selected, the part time indicator will be illuminated. The indicator remains illuminated until the cluster receives a part time 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 part time 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 part time lamp-ON and lamp-OFF messages to the instrument cluster. For further diagnosis of the part time indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the transfer case switch, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the part time indicator, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.
Full Time Indicator
A full time indicator is standard equipment on all instrument clusters, but is only functional on vehicles equipped with the optional Selec-Trac four-wheel drive system. The full time indicator is located near the lower edge of the tachometer dial face in the instrument cluster. The full time indicator consists of a stencil-like cutout of the words "FULL TIME" in the opaque layer of the instrument cluster overlay The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. A green Light Emitting Diode (LED) behind the cutout in the opaque layer of the cluster overlay causes the "FULL TIME" text to appear in green through the translucent outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board. When the exterior lighting is turned ON, the illumination intensity of the full time indicator is dimmable, which is adjusted using the panel lamps dimmer control ring on the left control stalk of the multi-function switch. The full time indicator is serviced as a unit with the instrument cluster.
The full time indicator gives an indication to the vehicle operator that a four-wheel drive full time operating mode of the transfer case is selected. On vehicles equipped with the optional Selec-Trac four wheel drive system, the full time indicator lights when the transfer case is engaged in the 4 X 4 Full Time position. This indicator is controlled by a transistor on the instrument cluster electronic 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 configured for the type of transfer case in the vehicle using a DRBIII scan tool in order to provide proper operation of the full time indicator. The full time 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 full time indicator for the following reasons:
- Full Time Lamp-ON Message - Each time the cluster receives a full time lamp-ON message from the PCM indicating that a four-wheel drive full time position of the transfer case has been selected, the full time indicator will be illuminated. The indicator remains illuminated until the cluster receives a full time 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 full time 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 full time lamp-ON and lamp-OFF messages to the instrument cluster. For further diagnosis of the full time indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the transfer case switch, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the full time indicator, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.
Four Low Mode Indicator
A four low mode indicator is standard equipment on all instrument clusters. The four low mode indicator is located above the coolant temperature gauge and to the right of the speedometer in the instrument cluster. The four low mode indicator consists of a stencil-like cutout of the words "4 LO MODE" in the opaque layer of the instrument cluster overlay The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. An amber Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the "4 LO MODE" text to appear in amber through the translucent outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic circuit board. The four low mode indicator is serviced as a unit with the instrument cluster.
The four low mode indicator gives an indication to the vehicle operator that a four-wheel drive low operating mode of the transfer case is selected. On vehicles equipped with the standard Command-Trac four- wheel drive system, the four low mode indicator lights when the transfer case is engaged in the 4L position. On vehicles equipped with the optional Selec-Trac four-wheel drive system, the four low mode indicator lights when the transfer case is engaged in the 4 Lo position. This indicator is controlled by a transistor on the instrument cluster electronic 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 configured for the type of transfer case in the vehicle using a DRBIII 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 Lamp-ON Message - Each time the cluster receives a four low mode lamp-ON message from the PCM indicating that a four-wheel drive low position of the transfer case has been selected, the four low mode indicator will be illuminated. The indicator remains illuminated until the cluster receives a four low mode 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 four low mode lamp-ON and lamp-OFF messages to the instrument cluster. For further diagnosis of the four low mode indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the transfer case switch, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the four low mode indicator, a DRBIII scan tool is required. Refer to the appropriate diagnostic information.