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Fuel Gauge Always Indicates Full (Dual Tank Diesel)

  1. Disconnect fuel pump and balance module connector. Using a fused jumper wire, connect module harness connector terminal "F" (Purple wire) to ground. Turn ignition on. If fuel gauge does not indicate empty, go to next step. If fuel gauge indicates empty, go to step  3.
  2. Disconnect IPC connector. Using DVOM, check continuity of Purple wire between IPC harness connector terminal No. 16 and module harness connector terminal "F". If continuity exists, replace IPC. If continuity does not exist, repair open on Purple wire and retest.
  3. Check continuity of Black/White wire between module harness connector terminal "E" and ground. If continuity exists, go to next step. If continuity does not exist, repair open on Black/White wire and retest.
  4. Check resistance between module harness connector terminals "E" (Black/White wire) and "B" (Light Blue wire). Resistance should be between zero ohms (empty) and 90 ohms (full). If resistance is not as specified, go to next step. If resistance is as specified, go to step  7.
  5. Disconnect secondary sending unit connector. Check resistance between sending unit terminals "A" and "D". Resistance should be between zero ohms (empty) and 90 ohms (full). If resistance is as specified, go to next step. If resistance is not as specified, replace secondary sending unit and retest.
  6. Check continuity of Black/White wire between module harness connector terminal "E" and secondary fuel sending unit harness connector terminal "A". See WIRING DIAGRAMS . If continuity exists, repair open on Light Blue wire between module harness connector terminal "B" and sending unit harness connector terminal "D". If continuity does not exist, repair open on Black/White wire and retest.
  7. Check resistance between module harness connector terminals "E" (Black/White wire) and "C" (Dark Blue/White wire). Resistance should be between zero ohms (empty) and 90 ohms (full). If resistance is not as specified, go to next step. If resistance is as specified, replace fuel pump and balance module.
  8. Disconnect primary sending unit connector. Check resistance between sending unit terminals "A" and "B". Resistance should be between zero ohms (empty) and 90 ohms (full). If resistance is as specified, go to next step. If resistance is not as specified, replace primary sending unit and retest.
  9. Check continuity of Black/White wire between module harness connector terminal "E" and primary fuel sending unit harness connector terminal "A". See WIRING DIAGRAMS . If continuity exists, repair open on Dark Blue/White wire between module harness connector terminal "C" and sending unit harness connector terminal "B". If continuity does not exist, repair open on Black/White wire and retest.
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