Test C: Fuel Level Reads Inaccurately

Check fuel gauge, see FUEL GAUGE under COMPONENT TESTS. Is the fuel gauge okay? If yes, go to next step. If no, replace fuel gauge. See FUEL GAUGE under REMOVAL & INSTALLATION.
Check fuel level sensor, see FUEL LEVEL SENSOR under COMPONENT TESTS. Is the fuel level sensor okay? If yes, go to next step. If no, replace fuel level sensor. See FUEL LEVEL SENSOR (SENDING UNIT) under REMOVAL & INSTALLATION.
Check fuel pump assembly ground. Turn key OFF. Locate and disconnect the fuel pump assembly connector. See Fig 1 . Measure the resistance of the Black wire between the fuel pump assembly connector and ground. See WIRING DIAGRAMS . Is the resistance less than 5 ohms? If yes, go to next step. If no, service Black wire.

Fig 1: Locating Fuel Pump Electrical Connector
Courtesy of FORD MOTOR CO.
Check wire between instrument cluster and fuel pump assembly. Turn key OFF. Disconnect the instrument cluster connector C270. Disconnect the fuel pump assembly connector. Measure the resistance of the Blue/Red wire between the instrument cluster connector C270 and the fuel pump assembly connector. See WIRING DIAGRAMS . Is the resistance less than 5 ohms? If yes, go to next step. If no, service Blue/Red wire.
Check for short between instrument cluster and fuel pump assembly. Turn key OFF. Disconnect the instrument cluster connector C270. Disconnect the fuel pump assembly connector. Measure the resistance of the Blue/Red wire between the instrument cluster connector C270 and ground. See WIRING DIAGRAMS . Is the resistance greater than 10,000 ohms? If yes, go to next step. If no, service Blue/Red wire.

NOTE: Fuel indicator module is also known as the anti-slosh module.

Check fuel indicator module. Turn key OFF. Disconnect all of the instrument cluster connectors. Using a jumper, connect Pin No. 2 of the fuel indicator module to the battery positive terminal. See Figure . Using a jumper, connect Pin No. 3 of the fuel indicator module to the battery negative terminal. Connect Rotunda Instrument Gauge System Tester (021-00055) or equivalent between Pin No. 5 of the fuel indicator module and the battery negative terminal. Measure the voltage on Pin No. 4 of the fuel indicator module at the specified conditions. See FUEL INDICATOR MODULE RESISTANCE table. Are the voltage readings (approximately) as specified? If yes, replace instrument cluster printed circuit. See INSTRUMENT CLUSTER PRINTED CIRCUIT under REMOVAL & INSTALLATION. If no, replace fuel indicator module. See FUEL INDICATOR MODULE under REMOVAL & INSTALLATION.