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Test D: Fuel Level Always Reads Full

  1. 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.
  2. 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.
  3. Check fuel pump assembly ground. Turn key OFF. Locate and disconnect the fuel pump assembly connector. See Figure . 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.
  4. Check wire between instrument cluster and fuel pump assembly. Turn key OFF. Disconnect the instrument cluster connector C270. Disconnect the fuel pump assembly connector. See WIRING DIAGRAMS  . Measure the resistance of the Blue/Red wire between the instrument cluster connector C270 and the fuel pump assembly connector. Is the resistance less than 5 ohms? If yes, go to next step. If no, service Blue/Red wire .
  5. Check power supply to fuel indicator module. Turn key OFF. Reconnect the instrument cluster connector C270. Remove the fuel indicator module from the back of the instrument cluster. Turn key ON. Measure the voltage on Pin No. 2 of the fuel indicator module connector on the back of the instrument cluster. See Figure . Is the voltage greater than 10 volts? If yes, go to next step. If no, see step  4 of TEST A: INTEGRATED CIRCUIT DISPLAY(S) INOPERATIVE OR ERRATIC  .
  6. Check fuel indicator module to ground. Turn key OFF. Reconnect the instrument cluster connector C270. Remove the fuel indicator module from the back of the instrument cluster. Measure the resistance between Pin No. 3 of the fuel indicator module connector and ground. Is the resistance less than 5 ohms? If yes, go to next step. If no, see step  4 of TEST A: INTEGRATED CIRCUIT DISPLAY(S) INOPERATIVE OR ERRATIC  .
  7. 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 following 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.
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