Operation

OPERATION

The service exhaust indicator gives an indication to the vehicle operator when the diesel exhaust particulate filter is clogged, requiring service or replacement. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received over the Controller Area Network (CAN) data bus from the Powertrain Control Module (PCM).

The service exhaust indicator function of the reconfigurable dot matrix Organic Light Emitting Diode (OLED) display unit 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 OLED service exhaust indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the service exhaust indicator for the following reasons:

- Service Exhaust Indicator Lamp-On Message - Each time the cluster receives an electronic service exhaust indicator lamp-ON message from the PCM indicating the diesel exhaust particulate filter is clogged, the service exhaust indicator will be illuminated. The indicator remains illuminated for about five seconds, until the cluster receives a lamp-OFF message from the PCM, until the cluster arbitrator logic determines that another display request has priority, or until the ignition switch is turned to the OFF position, whichever occurs first.

The PCM continually monitors a diesel engine particulate filter differential pressure sensor to determine the condition of the particulate filter. The PCM then sends the proper lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN).

For proper diagnosis of the diesel engine particulate filter system, the differential pressure sensor, the PCM, the EMIC, the CAN data bus or the electronic communication related to service exhaust indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.