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Test C: Fuel Gauge Inaccurate (With Flex Fuel)

NOTE: Perform all voltage and resistance tests using an Digital Volt-Ohm Meter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.
  1. Turn ignition switch to LOCK position. Disconnect fuel pump module 4-pin harness connector C434, located at center rear, under car. See Figure. Connect instrument gauge system tester (014-R1063) to fuel pump module harness connector C434 terminals No. 2 (Yellow/White wire) and No. 3 (Black/Yellow wire). See Figure. See WIRING DIAGRAMS . Set tester to 115 ohms. Turn ignition switch to RUN position. Turn tester power switch to ON position and wait for one minute. Fuel gauge should read FULL or above. Turn ignition switch to LOCK position. Set tester to 11 ohms. Turn ignition switch to RUN position and wait for one minute. Fuel gauge should read EMPTY or below. If fuel gauge operates correctly, go to next step. If fuel gauge does not operate correctly, go to step  4.
  2. Inspect fuel tank for any damage or deformation. If fuel tank is okay, go to next step. If fuel tank is faulty, replace fuel tank. See FUEL GAUGE SENDING UNIT  under REMOVAL & INSTALLATION. After repair, test system for normal operation.
  3. Remove fuel pump assembly from fuel tank. SeeFUEL GAUGE SENDING UNIT  under REMOVAL & INSTALLATION. Inspect fuel pump assembly for damage to wiring or connectors. Inspect float and float rod for damage or obstruction. If fuel pump and wiring are okay, replace fuel level sensor. If fuel pump or wiring is faulty, repair as necessary. After repair, test system for normal operation.
  4. Turn ignition switch to LOCK position. Disconnect flex fuel sensor module 6-pin harness connector C2005, located behind instrument cluster. See Figure. Measure resistance between fuel pump module harness connector C434 terminals No. 3 and flex fuel sensor module harness connector C2005 terminal No. 3 (Black/Yellow wire). See Figure and Fig 1 . See WIRING DIAGRAMS . Also measure resistance between ground and flex fuel sensor module harness connector C2005 terminals No. 3 (Black/Yellow wire). Resistance should be less than 5 ohms at measurement between fuel pump module and flex fuel sensor module, and more than 10 k/ohms at measurement between ground and flex fuel sensor module. If resistances are as specified, go to next step. If any resistance is not as specified, repair open or short circuit in Black/Yellow wirebetween fuel pump module and flex fuel sensor module. After repair, test system for normal operation.
  5. Measure resistance between fuel pump module harness connector C434 terminal No. 2 and flex fuel sensor module harness connector C2005 terminal No. 4 (Yellow/White wire). See Figure and Fig 1 . See WIRING DIAGRAMS . Also measure resistance between ground and fuel pump module harness connector C434terminal No. 2 (Yellow/White wire). Resistance should be less than 5 ohms at measurement between fuel sending unit and flex fuel sensor module, and more than 10 k/ohms at measurementbetween ground and flex fuel sensor module. If resistances are as specified, go to next step. If any resistance is not as specified, repair open or short circuit in Yellow/White wirebetween flex fuel sensor module and fuel pump module. After repair, test system for normal operation.
  6. Connect instrument gauge system tester (014-R1063) between ground and flex fuel sensor module harness connector C2005 terminal No. 6 (Orange/Light Green wire). Set tester to 145 ohms. Turn ignition switch to RUN position. Turn tester power switch to ON position and wait one minute. Fuel gauge should read FULL or above. Turn ignition switch to LOCK position. Set tester to 22 ohms. Turn ignition switch to RUN position and wait one minute. Fuel gauge should read EMPTY or below. If fuel gauge does not operate correctly, go to next step. If fuel gauge operates correctly, go to step  9.
  7. Turn ignition switch to LOCK position. Disconnect instrument cluster 16-pin harness connector C220a, located behind instrument cluster. See Figure. It may be necessary to remove instrument cluster to access connectors. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Measure resistance between instrument cluster harness connector C220a terminal No. 7 and flex fuel sensor module harness connector C2005 terminals No. 6 (Orange/Light Green wire). See Figure and Fig 1 . See WIRING DIAGRAMS . Also measure resistance between ground and instrument cluster harness connector C220a terminal No. 7 (Orange/Light Green wire). Resistance should be less than 5 ohms at measurement between instrument cluster and flex fuel sensor module, and more than 10 k/ohmsat measurement between ground and flex fuel sensor module. If resistances are as specified, go to next step. If any resistance is not as specified, repair open or short in Orange/Light Green wire between instrument clusterand fuel sensor module. After repair, test system for normal operation.
  8. Inspect instrument cluster printed circuit for contamination or damage. If instrument cluster printed circuit is okay, replace fuel gauge and fuel gauge indicator module. See FUEL GAUGE/TEMPERATURE GAUGE  under REMOVAL & INSTALLATION. If instrument cluster printed circuit is faulty, replace instrument cluster printed circuit. See PRINTED CIRCUIT  under REMOVAL & INSTALLATION. After repair, test system for normal operation.
  9. Turn ignition switch to LOCK position. Disconnect all flex fuel sensor module connectors. Flex fuel sensor module is located behind instrument cluster. See Figure. Check connectors for the following conditions, corrosion, pushed-out pins and see if connector is seated correctly. Correct any problems found. Operate system and verify if concern is still present. If concern still exist, replace flex fuel sensor module. If system is now operating correctly, concern may have been caused by a loose or corroded connector. After repair, test system for normal operation.
    Fig 1: Identifying Flexible Fuel Sensor Module Harness Connector C2005 Terminals
    G00013165Courtesy of FORD MOTOR CO.
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