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Home › GMC › 1999 › Forward Control 5.7 R, Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls - Basic Diagnostic Procedures › No Start Diagnosis › No Start-Engine Cranks Okay (3.4L) › Ignition System

Ignition System

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Install scan tool. Using scan tool, select FAILED SINCE CODE CLEAR function. If Diagnostic Trouble Codes (DTCs) P0101, P0123, P0601/P0602, P1200, P1374, P1626 or P1629 is present, diagnose DTCs. See appropriate SELF-DIAGNOSTICS article. If DTCs are not present, go to next step.
  3. Turn ignition on with engine off. Using scan tool, monitor Manifold Absolute Pressure (MAP) sensor. If MAP sensor value is less than 65 kPa, go to step  27. If MAP sensor value is 65 kPa or greater, go to next step.
  4. Turn ignition off. Disconnect Mass Airflow (MAF) sensor harness connector. Attempt to start engine. If engine starts and continues to run, go to step  27. If engine does not start, go to next step.
  5. Turn ignition off. Reconnect MAF sensor harness connector. Install fuel pressure gauge. Turn ignition on and observe fuel pressure. If fuel pressure is 41-47 psi (2.9-3.3 kg/cm2 ), go to step  7. If fuel pressure is not as specified, go to next step.
  6. If fuel pressure is present, but not as specified, diagnose fuel system. See BASIC FUEL SYSTEM CHECKS (GASOLINE ENGINES) . If fuel pressure is not present, go to FUEL SYSTEM ELECTRICAL CIRCUIT .
  7. Turn ignition off. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery positive, probe each fuel injector driver circuit while cranking engine. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light flashes for each circuit, go to next step. If test light does not flash for each circuit, go to step  9.
  8. Remove fuel injection fuse from underhood fuse block. Install Spark Tester (J-26792) to cylinders No. 2, 4 and 6 (one at a time). Connect spark plug wire of companion cylinder to ground. Crank engine and observe spark tester. If spark is present, go to step  19. If spark is not present, go to step  11.
  9. Check fuse for fuel injector feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuse is open, check for an open or shorted circuits, or shorted fuel injectors. Repair as necessary. If circuits and fuel injectors are okay, go to next step.
  10. Check for open in fuel injector feed circuit or driver circuits. Check ignition main relay feed circuits. Check for open in ignition main relay ground circuit. Check for stuck open ignition main relay or corroded contacts. Repair as necessary. If circuits or relay are okay, go to step  31.
  11. Check fuse for Ignition Control Module (ICM) ignition feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuse is open, check for short to ground in ICM feed circuit, or short to power in IC control circuit. Repair as necessary. If fuse is okay, go to next step.
  12. Check for open in ICM feed and ground circuits. Repair as necessary. If circuits are okay, go to next step.
  13. Disconnect 2-wire 7X Crankshaft Position (CKP) sensor harness connector from ICM. Connect DVOM between CKP sensor harness connector terminals. Set DVOM to AC scale. Crank engine and observe DVOM. DVOM should indicate about 2 volts. If voltage is as specified, go to step  15. If voltage is not as specified, go to next step.
  14. Turn ignition off. Check 7X CKP sensor circuit for open or short to power or ground. Check for poor 7X CKP sensor connection or 7X wiring harness shorted together. Repair as necessary. If circuit is okay, go to step  28.
  15. Check for poor ICM connections. Repair as necessary. If connections are okay, go to next step.
  16. Remove and inspect ignition coil(s) that did not produce a spark. Check for cracks or carbon tracking. Replace as necessary. If coil(s) are okay, go to next step.
  17. Using DVOM, measure secondary resistance of ignition coil that did not produce a spark. Resistance should be 5000-7000 ohms. If resistance is not as specified, replace ignition coil. If resistance is as specified, go to next step.
  18. Connect a test light across affected ICM primary terminals. See appropriate wiring diagram in WIRING DIAGRAMS article. Crank engine and observe test light. If test light flashes while cranking engine, go to step  29. If test light does not flash, go to step  30.
  19. Check spark plug wires for cylinders No. 2, 4 and 6. Check for carbon tracking or damaged insulation. Replace as necessary. If spark plug wires are okay, go to next step.
  20. Using DVOM, measure resistance of spark plug wires for cylinders No. 2, 4 and 6. Resistance should not be greater than 7000 ohms. If resistance is not as specified, replace wires. If wires are okay, go to next step.
  21. Remove spark plugs from cylinders No. 2, 4 and 6. Check spark plug electrodes for excessive fouling. If excessive fouling is present, go to step  26. If excessive fouling is not present, go to next step.
  22. Check spark plug wires for cylinders No. 1, 3 and 5. Check for carbon tracking or damaged insulation. Replace as necessary. If wires are okay, go to next step.
  23. Using DVOM, measure resistance of spark plug wires for cylinders No. 1, 3 and 5. Resistance should not be greater than 7000 ohms. If resistance is not as specified, replace wires. If wires are okay, go to next step.
  24. Remove spark plugs from cylinders No. 1, 3 and 5. Check spark plug electrodes for excessive fouling. If excessive fouling is present, go to step  26. If excessive fouling is not present, go to next step.
  25. Test fuel for contamination. If fuel is contaminated, clean fuel system. If fuel is not contaminated, check PCM for poor connections or damaged connectors. Check for faulty ECT sensor, or mass airflow sensor miscalculated due to faulty TP sensor or MAP sensor. See appropriate SYSTEM & COMPONENT TESTING article.
  26. Check for engine mechanical problem. Check for bent push rods, faulty camshaft, leaking or sticky valves or rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing or leaking head gasket. Repair as necessary.
  27. Replace MAP sensor.
  28. Replace 7X CKP sensor.
  29. Replace ignition coil(s) associated with cylinder that did not produce a spark.
  30. Replace ICM.
  31. Replace PCM. Perform PCM relearn procedures.
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