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Home >> Dodge and Ram >> 2002 >> RAM 3500 Van V8-5.2L CNG VIN T >> Repair and Diagnosis >> Instrument Panel, Gauges and Warning Indicators >> Instrument Cluster / Carrier >> Description and Operation >> Electro/Mechanical Instrument Cluster (EMIC) >> Indicators >> Part 2 of 2 >> Part 2A

Part 2A

HIGH BEAM INDICATOR
A high beam indicator is standard equipment on all instrument clusters The high beam indicator is located near the lower edge of the instrument cluster overlay, to the right of center. The high beam indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for "High Beam" 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 blue lens behind the cutout in the opaque layer of the overlay causes the icon to appear in blue through the translucent outer layer of the overlay when it is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The high beam indicator is serviced as a unit with the instrument cluster.

The high beam indicator gives an indication to the vehicle operator when the headlamp high beams are illuminated. This indicator is hard wired on the instrument cluster electronic circuit board, and is controlled by a headlamp beam select switch input to the cluster. The headlamp high beam indicator bulb receives a ground path on the instrument cluster electronic circuit board at all times; therefore, the indicator remains operational regardless of the ignition switch position. The headlamp beam select switch is integral to the multi-function switch on the left side of the steering column, and is connected in series between fused B(+) and the headlamp high beam indicator. The indicator bulb only illuminates when it is provided with battery current through the high beam indicator driver circuit by the headlamp beam select switch. (Refer to ELECTRICAL/LAMPS/LIGHTING - EXTERIOR/MULTI-FUNCTION SWITCH - OPERATION). The high beam indicator can be diagnosed using conventional diagnostic tools and methods.

LOW FUEL INDICATOR
A low fuel indicator is standard equipment on all instrument clusters. The low fuel indicator is located near the upper edge of the instrument cluster overlay, to the right of center. The low fuel indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for "Fuel" 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 lens behind the cutout in the opaque layer of the overlay causes the icon to appear in amber through the translucent outer layer of the overlay when the indicator is illuminated from behind by a Light Emitting Diode (LED) soldered onto the instrument cluster electronic circuit board. The low fuel indicator is serviced as a unit with the instrument cluster.

The low fuel indicator gives an indication to the vehicle operator when the level of fuel in the fuel tank becomes low. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Chrysler Collision Detection (CCD) data bus. The low fuel indicator Light Emitting Diode (LED) receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions; 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 low fuel indicator for the following reasons:
* Bulb Test - Each time the ignition switch is turned to the ON position the indicator is illuminated for about two seconds as a bulb test.
* Less Than 12.5 Percent Tank Full Message - Each time the cluster receives messages from the PCM indicating the percent tank full is 12.5 (one- eighth) or less for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, the low fuel indicator is illuminated and a single chime tone is sounded. The low fuel indicator remains illuminated until the cluster receives messages from the PCM indicating that the percent tank full is greater than 12.5 (one-eighth) for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the low fuel indicator is cycled OFF and then ON again by the appropriate percent tank full messages from the PCM.
* Less Than Empty Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full is less than empty, the low fuel indicator is illuminated immediately This message would indicate that the fuel tank sender input to the PCM is a short circuit.
* More Than Full Percent Tank Full Message - Each time the cluster receives a message from the PCM indicating the percent tank full is more than full, the low fuel indicator is illuminated immediately This message would indicate that the fuel tank sender input to the PCM is an open circuit.
* Actuator Test - Each time the cluster is put through the actuator test, the low fuel 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 fuel tank sending unit, then sends the proper messages to the instrument cluster. For further diagnosis of the low fuel indicator or the instrument cluster circuitry that controls the LED. For proper diagnosis of the fuel tank sending unit, the PCM, the CCD data bus, or the message inputs to the instrument cluster that control the low fuel indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.



MALFUNCTION INDICATOR LAMP (MIL)
A Malfunction Indicator Lamp (MIL) is standard equipment on all instrument clusters. The MIL is located near the lower edge of the instrument cluster overlay to the right of center. The MIL consists of a stencil-like cutout of the International Control and Display Symbol icon for "Engine" 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 lens behind the cutout in the opaque layer of the overlay causes the icon to appear in amber through the translucent outer layer of the overlay when the indicator is illuminated from behind by a Light Emitting Diode (LED) soldered onto the instrument cluster electronic circuit board. The MIL is serviced as a unit with the instrument cluster.

The Malfunction Indicator Lamp (MIL) gives an indication to the vehicle operator when the Power- train Control Module (PCM) has recorded a Diagnostic Trouble Code (DTC) for an On-Board Diagnostics II (OBDII) emissions-related circuit or component malfunction. The MIL is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the PCM over the Chrysler Collision Detection (CCD) data bus. The MIL bulb Light Emitting Diode (LED) receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions; 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 MIL for the following reasons:
* Bulb Test - Each time the ignition switch is turned to the ON position the indicator is illuminated for about seven seconds as a bulb test.
* PCM Lamp-ON Message - Each time the cluster receives a lamp-ON message from the PCM, the indicator will be illuminated. The indicator can be flashed ON and OFF or illuminated solid, as dictated by the PCM message. For some DTC's, if a problem does not recur, the PCM will send a lamp-off message automatically. Other DTC's may require that a fault be repaired and the PCM be reset before a lamp-off message will be sent. For more information on the PCM and the DTC set and reset parameters.
* Communication Error - If the cluster receives no lamp-ON message from the PCM for twenty seconds, the MIL is illuminated by the instrument cluster to indicate a loss of bus communication. The lamp remains controlled and illuminated by the cluster until a valid lamp-ON message is received from the PCM.
* Actuator Test - Each time the cluster is put through the actuator test, the indicator will be turned ON 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 fuel and emissions system circuits and sensors to decide whether the system is in good operating condition. The PCM then sends the proper lamp-ON or lamp-off messages to the instrument cluster. For further diagnosis of the MIL or the instrument cluster circuitry that controls the LED. If the instrument cluster turns ON the MIL after the bulb test, it may indicate that a malfunction has occurred and that the fuel and emissions systems may require service. For proper diagnosis of the fuel and emissions systems, the PCM, the CCD data bus, or the message inputs to the instrument cluster that control the MIL, a DRB III scan tool is required. Refer to the appropriate diagnostic information.






OVERDRIVE OFF INDICATOR
An overdrive off indicator is standard equipment on all instrument clusters.ON 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). The VFD is part of the cluster electronic circuit board, and is visible through a cutout located in the lower right corner of the cluster overlay. The dark lens of 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 it is 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 Chrysler Collision Detection (CCD) data bus. The overdrive off indicator receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run- start) circuit whenever the ignition switch is in the ON or Start positions; 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. For proper diagnosis of the overdrive control system, the PCM, the CCD data bus, or the 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.



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