Operation

OPERATION

The air cleaner indicator gives an indication to the vehicle operator when the air cleaner filter element has reached its service limit. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster over the Controller Area Network (CAN) data bus from the Engine Control Module (ECM) (also known as the Powertrain Control Module/PCM).

The air cleaner indicator Light Emitting Diode (LED) or icon and textual message display are completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate or icon and textual message to be displayed when the instrument cluster detects that the ignition switch is in the ON position. Therefore, the LED or the icon and textual message will always be OFF when the ignition switch is in any position except ON. The LED only illuminates or the icon and textual message is only displayed when it is activated by the instrument cluster logic. The instrument cluster will turn ON the air cleaner indicator for the following reasons:

- Bulb Test - On vehicles not equipped with the optional steering wheel buttons, each time the ignition switch is turned to the ON position the air cleaner indicator is illuminated by the cluster briefly as a bulb test.
- Air Cleaner Indicator Lamp-On Message - On vehicles not equipped with the optional steering wheel buttons, each time the cluster receives an electronic air cleaner indicator lamp-ON message from the ECM, the air cleaner indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the ECM, or until the ignition switch is turned to the OFF position, whichever occurs first. On vehicles equipped with the optional steering wheel buttons, each time the cluster receives an electronic air cleaner indicator lamp-ON message from the ECM, an icon and Air cleaner dirty textual message will appear within the cluster multi-function display. The icon and textual message remain displayed until the message is acknowledged by momentarily depressing one of the steering wheel or cluster buttons, until the cluster receives a lamp-OFF message from the ECM following a reset of the air cleaner counter using a diagnostic scan tool routine, or until the ignition switch is turned to the OFF position, whichever occurs first.

The ECM continually monitors engine operating time and vehicle distance to decide whether the air cleaner filter is in good operating condition. The ECM then sends the proper lamp-ON or lamp-OFF messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN or KOMBI). If the ECM sends a lamp-ON message after the bulb test, it indicates that the ECM has detected that the service limit for the air cleaner filter has been reached, which could result in the engine running poorly and producing excessive emissions. The ECM will store a Diagnostic Trouble Code (DTC) for any malfunction it detects.

For proper diagnosis of the ECM, the EMIC, the CAN data bus or the electronic communication related to air cleaner indicator operation, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.