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Fuel Injector Circuit Diagnosis (5.7L)

  1. Install scan tool. Start engine and let idle. Increase engine speed to 750 RPM. Using scan tool, monitor MISFIRE CUR. COUNTERS on MISFIRE DATA LIST (total of 8 counters, one per cylinder). If any MISFIRE CUR. COUNTERS are increasing, go to step  3. If no MISFIRE CUR. COUNTERS are increasing, go to next step.
  2. Monitor MISFIRE HIST. COUNTERS on MISFIRE DATA LIST. If any MISFIRE HIST. COUNTERS indicate a number other than zero, go to step  17. If all MISFIRE HIST. COUNTERS indicate zero, check for intermittent. An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect PCM harness connector for backed-out terminals, improper mating, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness. When injector driver is disabled, an engine misfire will be apparent and a misfire DTC will set. Freeze frame and/or failure records data may also assist in locating an intermittent condition.
  3. Check fuel injector ignition feed fuses. If all injector fuses are okay, go to next step. If any fuel injector fuse(s) is blown, go to step  7.
  4. Turn ignition off. Disconnect fuel injector harness connector that MISFIRE CUR COUNTER is increasing. Turn ignition on, leaving engine off. Using a test light connected to ground, probe ignition feed circuit (Pink wire) at appropriate fuel injector harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step  9.
  5. Turn ignition off. Connect fuel injector test light to fuel injector harness connector. Start engine. If test light blinks, go to next step. If test light does not blink, go to step  10.
  6. Check for poor connection at fuel injector harness terminals. If a problem exists, repair as necessary and go to step  18. If a problem does not exist, go to step  14.
  7. Turn ignition off. Disconnect the 4 fuel injector harness connectors related to fuse that was blown. Using a test light connected to battery voltage, probe one fuel injector ignition feed circuit (Pink wire). If test light does not illuminate, go to next step. If test light illuminates, go to step  12.
  8. Using DVOM, measure resistance of each fuel injector that is powered by blown fuse. If resistance is greater than 11.4 ohms at any fuel injector, go to step  13. If resistance is 11.4 or less ohms at any fuel injector, go to step  14.
  9. Repair open in appropriate fuel injector ignition feed circuit (Pink wire). After repairs, go to step  18.
  10. Turn ignition off. Disconnect PCM harness connector C1. Check for an open or short to ground in fuel injector control circuits between PCM and fuel injector harness connectors. If problem exists, go to next step. If problem does not exist, go to step  15.
  11. Repair open or short to ground in fuel injector control circuit. After repairs, go to step  18.
  12. Repair short to ground in appropriate fuel injector ignition feed circuit. After repairs, go to step  18
  13. Repair intermittent short to ground in appropriate fuel injector ignition feed circuit. After repairs, go to step  18
  14. Replace faulty injector(s) as necessary. After repairs, go to step  18
  15. Check for poor connections at PCM. If problem exists, repair as necessary and go to step  18. If problem does not exist, go to next step.
  16. Replace PCM. After repairs, go to step  18.
  17. Inspect appropriate injector circuit for poor connection at injector and PCM, intermittent short to ground, and intermittent opens. If problem exist, repair as necessary and go to step  18. If problem does not exist, repair by symptom. See appropriate TROUBLE SHOOTING - NO CODES article.
  18. Using scan tool, clear DTCs. Start engine and let idle. Using scan tool, select DIAGNOSTIC TROUBLE CODE (DTC) option, and then SPECIFIC DTC option. Enter DTC and operate vehicle within conditions for running the DTC. If scan tool indicates DTC ran and passed, go to next step. If scan tool does not indicate DTC ran and passed, go to step  1.
  19. Using scan tool, select CAPTURE INFO option, and then REVIEW INFO option. If no DTCs are set, system is okay. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
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