Water In Fuel Indicator

The water-in-fuel indicator gives an indication to the vehicle operator when there is excessive water detected in the diesel fuel. This indicator is controlled by the CCN based upon programming and electronic messages received from the PCM over the CAN data bus.

The water-in-fuel indicator LED is completely controlled by the 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 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 CCN transistor. The CCN will illuminate the water-in-fuel indicator for the following reasons:

• Water-In-Fuel Indicator Lamp-ON Message  - Each time the CCN receives an electronic water-in-fuel indicator lamp-ON  message from the PCM indicating there is excessive water in the diesel fuel system, the water-in-fuel indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the PCM, or until the ignition switch is turned to the OFF position, whichever occurs first.

The PCM continually monitors the water-in-fuel sensor to determine whether there is excessive water in the diesel fuel system. The PCM then sends the proper electronic water-in-fuel  message to the CCN.