Dakota Quad Cab 2WD V8-5.9L VIN Z LDC (2002)
Overdrive Indicator Lamp: Description and Operation
OVERDRIVE OFF INDICATOR
An overdrive OFF indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with the optional overdrive automatic
transmission, this indicator is electronically disabled. The overdrive OFF indicator consists of the text "O/D OFF", which appears in the lower portion of
the electronic gear selector indicator Vacuum Fluorescent Display (VFD) unit.
The VFD is part of the cluster electronic circuit board and is visible through a window with a smoked clear lens located in the lower right corner of the
cluster overlay. The dark lens over the VFD prevents the indicator from being clearly visible when it is not illuminated. The text "O/D OFF" appears in
an amber color and at the same lighting level as the gear selector indicator information when they are illuminated by the instrument cluster electronic
circuit board. The overdrive OFF indicator is serviced as a unit with the VFD in the instrument cluster.
The overdrive OFF indicator gives an indication to the vehicle operator when the OFF position of the overdrive OFF switch has been selected, disabling
the electronically controlled overdrive feature of the automatic transmission. This indicator is controlled by the instrument cluster circuit board based
upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable
Communications Interface (PCI) data bus.
The overdrive OFF indicator 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 indicator will always be
OFF when the ignition switch is in any position except ON or Start. The indicator only illuminates when it is switched to ground by the instrument
cluster circuitry The instrument cluster will turn ON the overdrive OFF indicator for the following reasons:
Bulb Test - Each time the ignition switch is turned to the ON position the overdrive OFF indicator is illuminated for about two seconds as a bulb test.
Overdrive OFF Lamp-ON Message - Each time the cluster receives an overdrive OFF lamp-ON message from the PCM indicating that the OFF
position of the overdrive OFF switch has been selected, the overdrive OFF indicator will be illuminated. The indicator remains illuminated until the
cluster receives an overdrive OFF 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 overdrive OFF indicator will be turned ON, then OFF again during the VFD
portion of the test to confirm the functionality of the VFD, and again during the bulb check portion of the test to confirm the functionality of the cluster
control circuitry
The PCM continually monitors the overdrive OFF switch to determine the proper outputs to the automatic transmission. The PCM then sends the proper
overdrive OFF lamp-ON and lamp-OFF messages to the instrument cluster. For further diagnosis of the overdrive OFF indicator or the instrument cluster
circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the overdrive control
system, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the overdrive OFF indicator, a DRB III scan
tool is required. Refer to the appropriate diagnostic information
