Low Fuel Indicator: Operation

WARNING: This page is about a different car, the 2006 Dodge Sprinter. However, it is still accessible from the selected car via links, so may be relevant.

The low fuel indicator gives an indication to the vehicle operator when the level of fuel in the fuel tank becomes low. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and a hard wired input received by the cluster from the fuel level sensor in the fuel tank. The low fuel indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster detects that the ignition switch is in the On position. Therefore, the LED will always be off when the ignition switch is in any position except On. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn on the low fuel indicator for the following reasons:

Bulb Test - Each time the ignition switch is turned to the On position the low fuel indicator is illuminated for about two seconds as a bulb test.
Fuel Level Sensor Input - Each time the cluster receives an input from the fuel level sensor indicating that the fuel level has reached about 12 liters (3 gallons) or less, the low fuel indicator is illuminated. The indicator remains illuminated until the cluster receives an input from the fuel level sensor indicating that the fuel level is above 12 liters (3 gallons), or until the ignition switch is turned to the Off position, whichever occurs first.

The fuel level sensor in the fuel tank provides a hard wired input to the instrument cluster circuitry through the fuel level sense circuit. The fuel level sensor is a potentiometer that changes resistance according to the fuel level. As the fuel level decreases, the resistance through the fuel level sensor increases. The instrument cluster applies a fuel tank characteristic curve and fuel tank reserve valve setting to the fuel level sensor input, which must be configured when the cluster is initialized. These characteristics determine the algorithm the cluster uses to display the fuel level data on the fuel gauge and the control for the low fuel warning indicator. The fuel level sensor and the fuel level sense circuit to the instrument cluster can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the instrument cluster circuitry that controls the fuel gauge, a diagnostic scan tool is required. Refer to BODY DIAGNOSTIC PROCEDURES .