Fuel Gauge System

DIAGNOSTIC AIDS
CAUTION: The following actions or conditions will cause damage to and require replacement of the electronic fuel gauge.
^ Applying battery voltage to the low fuel warning lamp to test bulb operation. The lamp should be checked with an ohmmeter to verify continuity.
^ An open in the warning lamp tier ground circuit.
^ Inadvertent installation of a low fuel warning module that is not required on vehicles equipped with the electronic cluster.

NOTE: If an open or short circuit condition exists when the ignition switch is turned to the RUN or ACC position, the gauge will show the alert at the conclusion of the prove out.

Fuel Gauge Open And Short Circuit Conditions:

OPEN CIRCUIT CONDITIONS
If an OPEN circuit exists between the fuel sender and the fuel gauge, the E, F, and grads will flash continuously at a one cycle per second rate. All bars will be OFF. The OPEN circuit alert will continue to flash until the condition has been corrected. It may take up to three minutes for the gauge to detect the open circuit, and up to one minute for the gauge to recover after the condition is corrected.

SHORT CIRCUIT CONDITIONS
If the fuel sender to the fuel gauge circuit is SHORTED to ground, the fuel bar segments will flash at on cycle per second rate with the E, F, ISO and grads turned OFF. The SHORT circuit alert will continue until the shorted condition is corrected. It may take the gauge up to two minutes to detect the shorted condition, and up to one minute for the gauge to recover after the condition is corrected.

PRELIMINARY CHECKS
1. Visually inspect fuel tank for damage. A fuel tank that is collapsed or distorted from its normal shape will seriously affect the fuel indicating system operation.
2. If a vehicle is encountered where the fuel tank does not fill completely. This will result in the fuel gauge not reaching the FULL mark. Check by shaking the vehicle after the first pump nozzle cutoff and then slowly meter fuel into the tank with the shut off nozzle withdrawn to the edge of the filler neck. If the fuel gauge reaches FULL after this procedure, the tank will not fill because of the fuel tank or filling practices and will not be corrected by replacement of the fuel indicating system components.
3. Verification of proper failure mode is important before undertaking any diagnostic procedures. The following are possible failure modes of electronic fuel gauge system.
^ Fuel gauge display does not illuminate.
^ All bars flash.
^ E, F, and grad symbols continue to flash.
^ Fuel tank display does not correspond with the fuel level in the tank.
^ Erratic fuel display. Fuel level indication is different by more than +/- two bars after each time ignition switch key is turned to the ON or ACC position while standing still.
^ Fuel gauge display illumination cannot be regulated with headlamp switch rheostat.
^ Fuel gauge display dim as compared to other displays in the cluster.