Part 2 of 8
ABS SYSTEM INDICATORAn Antilock Brake System (ABS) indicator lamp is standard equipment on all instrument clusters, but is only functional on vehicles equipped with the ABS option. The ABS indicator lamp is located near the lower edge of the instrument cluster overlay, to the left of the odometer/trip odometer Vacuum-Fluorescent Display (VFD). The ABS indicator lamp consists of a hybridized version of the International Control and Display Symbol icon for brake, but with the acronym "ABS" located in the center of the icon. This icon is a stenciled cutout in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the icon from being clearly visible when the lamp 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 it is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The ABS indicator lamp is serviced as a unit with the instrument cluster.
The ABS indicator lamp gives an indication to the vehicle operator when the ABS system is faulty or inoperative. This lamp is hard wired on the instrument cluster electronic circuit board, and is completely controlled by the Controller Antilock Brake (CAB). The ABS indicator lamp bulb receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (st-run) circuit whenever the ignition switch is in the ON or Start positions; therefore, the lamp will always be OFF when the ignition switch is in any position except ON or Start. The lamp bulb only illuminates when it is provided a path to ground by the CAB through the CAB relay ill the Power Distribution Center (PDC). The CAB continually monitors the ABS circuits and sensors to decide whether the system is in good operating condition. The lamp is turned ON by the CAB for about two seconds after the ignition switch is turned to the ON position as a bulb test. After the bulb test, the CAB turns the lamp ON or OFF based upon the results of the ABS self-tests. If the CAB turns the lamp ON after the bulb test, it indicates that the CAB has detected a system malfunction and/or that the ABS system has become inoperative. The ABS indicator lamp can be diagnosed using conventional diagnostic tools and methods.
AIRBAG INDICATOR
An airbag indicator lamp is standard equipment on all instrument clusters, but is electronically disabled on vehicles not equipped with airbags. The airbag indicator lamp is located near the lower edge of the instrument cluster overlay, to the right of the odometer/trip odometer Vacuum-Fluorescent Display (VFD). The airbag indicator lamp consists of a stenciled cutout of the word "AIRBAG" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when the lamp is not illuminated. A red lens behind the cutout in the opaque layer of the overlay causes the "AIRBAG" text to appear in red 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 airbag indicator lamp is serviced as a unit with the instrument cluster.
The airbag indicator lamp gives an indication to the vehicle operator when the airbag system is faulty or inoperative. This lamp 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 Airbag Control Module (ACM) over the Chrysler Collision Detection (CCD) data bus. The airbag indicator lamp bulb receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (st-run) circuit whenever the ignition switch is in the ON or Start positions; therefore, the lamp will always be OFF when the ignition switch is in any position except ON or Start. The lamp bulb only illuminates when it is switched to ground by the instrument cluster transistor. The instrument cluster will turn ON the airbag indicator lamp for the following reasons:
- Bulb Test - Each time the ignition switch is turned to the ON position the lamp is illuminated for about seven seconds.
- ACM Lamp-ON Message - Each time the cluster receives two consecutive lamp-ON messages from the ACM, the lamp will be illuminated. The lamp remains illuminated for about twelve seconds or until the cluster receives two consecutive lamp-OFF messages from the ACM, whichever is longer.
- Communication Error - If the cluster receives no airbag messages for five consecutive seconds, or if the messages received have an improper check sum, the lamp is illuminated. The lamp remains illuminated for about twelve seconds or until the cluster receives a single lamp-OFF message from the ACM, whichever is longer.
- Actuator Test - Each time the cluster is put through the actuator test, the lamp will be turned ON and OFF in a prescribed sequence to confirm the functionality of the lamp and the cluster circuitry.
The ACM continually monitors the airbag system circuits and sensors to decide whether the system is in good operating condition. The ACM then sends the proper lamp-ON or lamp-OFF messages to the instrument cluster. If the airbag indicator lamp fails to light during the bulb test, replace the bulb with a known good unit. For further diagnosis of the airbag indicator lamp or the instrument cluster circuitry that controls the lamp, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). If the instrument cluster turns ON the airbag indicator lamp after the bulb test, it may indicate that a malfunction has occurred and that the airbags may not deploy when required or may deploy when not required. In addition, if the airbag indicator lamp or the transistor that energizes the lamp are inoperative, the instrument cluster will send an electronic fault message to the ACM. For proper diagnosis of the airbag system, the CCD data bus, or the message inputs to the instrument cluster that control the airbag indicator lamp, a DRB III scan tool and the appropriate diagnostic information are required.
BRAKE/PARK BRAKE INDICATOR
A brake indicator lamp is standard equipment on all instrument clusters. The brake indicator lamp is located near the lower edge of the instrument cluster overlay, to the left of the odometer/trip odometer Vacuum-Fluorescent Display (VFD). The brake indicator lamp consists of a red lens behind a rectangular cutout in the instrument cluster overlay. The word "BRAKE" is imprinted in bold black lettering near the center of the red lens. The word "BRAKE" is clearly visible on the face of the instrument cluster when the lamp is not illuminated, and is silhouetted in a bright red glow on the face of the instrument cluster when the brake indicator lamp is illuminated from behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The brake indicator lamp is serviced as a unit with the instrument cluster.
The brake indicator lamp gives an indication to the vehicle operator when the parking brake is applied, or when there are certain brake hydraulic system malfunctions. This lamp is hard wired on the instrument cluster electronic circuit board, and is controlled by three switch inputs to the cluster. The brake indicator lamp bulb receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (st-run) circuit whenever the ignition switch is in the ON or Start positions; therefore, the lamp will always be OFF when the ignition switch is in any position except ON or Start. The brake indicator lamp will be illuminated under the following conditions:
- Bulb Test - Each time the ignition switch is turned to the Start position the lamp is illuminated as a bulb test.
- Park Brake-ON - If the park brake is applied with the ignition switch in the ON position, the lamp is illuminated.
- Brake Hydraulic System Malfunction - If the pressures in the two halves of the split brake hydraulic system are unequal with the ignition switch in the ON position, the lamp is illuminated.
The hard wired inputs to the brake indicator lamp include:
- Ignition Switch - A contact in the ignition switch provides a ground path to the red brake warning indicator driver circuit whenever the ignition switch is turned to the Start position.
- Park Brake Switch - The park brake switch on the park brake lever mechanism provides a ground path to the red brake warning indicator driver circuit whenever the park brake is applied.
- Brake Warning Pressure Switch - The brake warning pressure switch on the brake combination valve provides a ground path to the red brake warning indicator driver circuit whenever the switch is closed by a pressure differential Spool valve within the combination valve unit.
The ignition switch, the park brake switch, and the brake warning pressure switch are each connected in parallel between ground and the red brake warning indicator input to the instrument cluster so that each of their inputs will illuminate the lamp independently of the others. The brake indicator lamp can be diagnosed using conventional diagnostic tools and methods.