Fuel Gauge

The fuel gauge gives an indication to the vehicle operator of the level of fuel in the fuel tank. This gauge is controlled by the Instrument Cluster (IC) (also known as the Instrument Panel Cluster/IPC) electronic circuit board based upon programming and electronic messages received from the Body Control Module (BCM) over the CAN data bus.

The fuel gauge is an electronic bar graph gauge within the IC electronic display unit that receives battery current on the IC electronic circuit board through a fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The electronic display unit will not display this bar graph after the ignition switch is turned to the OFF position. The IC circuitry controls the bar graph display and provides the following features:

• Fuel Level Message  - Following the ignition ON event, the bar graph is illuminated in a progressive fashion beginning at the bottom segment and working towards the top segment in a manner that is linear to the fuel level indicated by the electronic fuel level  message received by the IC from the BCM over the CAN data bus.
• Less Than 10 Percent Tank Full Message  - Each time the IC receives a fuel level message that indicates the fuel tank is about 10 percent full or less and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, the appropriate gauge bar graph segment is illuminated (about the one-sixteenth graduation on the bar graph) and the BCM also sends electronic messages to the IC to illuminate the low fuel indicator and sound a single chime tone. The low fuel indicator remains illuminated until the fuel level input indicates that the fuel tank is greater than about 13 percent full for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the low fuel indicator is cycled OFF and then ON again by the appropriate messages from the BCM.

The BCM provides a constant current source to the fuel level sending unit and monitors a return input on a fuel level sense circuit. The resistance through the fuel level sending unit increases as the fuel level rises and decreases as the fuel level falls causing changes in the fuel level sense input voltage. The BCM then sends the appropriate electronic fuel level  messages to the IC. The BCM programming applies an algorithm to calculate the proper fuel gauge position based upon the fuel level message input, then sends electronic messages to the IC to illuminate the proper segments on the gauge bar graph. This algorithm is used to dampen bar graph segment movement against the negative effect that fuel sloshing within the fuel tank can have on accurate inputs from the fuel tank sending unit to the BCM.

For proper diagnosis of the fuel level sending unit, the BCM, the IC, the CAN data bus or the electronic communication related to fuel gauge operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.