Operation
OPERATION
The water-in-fuel indicator gives an indication to the vehicle operator when there is excessive water detected in the fuel filter. 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 water-in-fuel indicator Light Emitting Diode (LED) or icon and textual message display is 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 water-in-fuel 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 water-in-fuel indicator is illuminated by the cluster briefly as a bulb test.
- Water-In-Fuel Indicator Lamp-On Message - On vehicles not equipped with the optional steering wheel buttons, each time the cluster receives an electronic water-in-fuel indicator lamp-ON message from the ECM indicating that there is excessive water in the fuel filter with the engine running, the water-in-fuel 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 water-in-fuel indicator lamp-ON message from the ECM, an icon and Water in Fuel - Visit workshop 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 the draining of excess water from the fuel filter, or until the ignition switch is turned to the OFF position, whichever occurs first.
The ECM continually monitors the water-in-fuel sensor to determine whether there is excessive water in the fuel filter. 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 water-in-fuel indicator remains illuminated with the engine running, excess water should be drained from the fuel filter. If the indicator remains illuminated with the engine running after the excess water has been drained from the fuel filter, it may indicate that a malfunction has occurred in the water-in-fuel sensor or circuits. The ECM will store a Diagnostic Trouble Code (DTC) for any malfunction it detects.
For proper diagnosis of the water-in-fuel sensor and circuits, the ECM, the EMIC, the CAN data bus or the electronic communication related to water-in-fuel indicator operation, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.