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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Basic Diagnostic Procedures >> No-Start Diagnosis >> No-Start - Engine Cranks Okay (4.2L) >> Diagnostic Procedure

Diagnostic Procedure

  1. Perform OBD system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. After performing OBD system check, go to next step.
  2. Turn ON the ignition, with the engine OFF. With scan tool, observe DTC information. Does scan tool display DTC P0107, P0601, P0602, P0604, P0606, P0607, P1220, P1221, P1271, P1514, P1621, P1631, P1635, P1639, P1680, P1681, or P1683? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article. If no, go to next step.
  3. Monitor Ignition 1 Signal Voltage parameter with scan tool. Does Ignition 1 Signal Voltage parameter read battery voltage? If yes, go to next step. If no, go to step  10.
  4. Command fuel pump ON with scan tool. Does fuel pump turn ON? If yes, go to next step. If no, go to FUEL PUMP RELAY (ALL EXCEPT 2.2L & 3.0L VUE, 3.4L, 5.0L & 5.7L) under FUEL SYSTEM (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  5. Turn OFF the ignition. Remove an ignition coil. Install (J 26792) Spark Tester to coil boot. Attempt to start engine. Does spark tester spark? If yes, go to next step. If no, go to ELECTRONIC IGNITION SYSTEM DIAGNOSIS (4.2L) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  6. Turn OFF the ignition. Disconnect fuel injector harness multi-way connector. Probe a fuel injector control circuit, PCM side, with test light connected to battery voltage. Crank engine. Does test light flash when cranking engine? If yes, go to next step. If no, go to FUEL INJECTOR CIRCUIT DIAGNOSIS (4.2L) under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article.
  7. Turn OFF the ignition. Install (J 34730-1A) Fuel Pressure Gauge. Turn ON the ignition, with the engine OFF. Command fuel pump ON with scan tool. Is fuel pressure within 48-52 psi (334-375 kPa) while fuel pump is operating? If yes, go to next step. If no, go to FUEL SYSTEM PRESSURE TEST (4.2L)  under BASIC FUEL SYSTEM CHECKS (GASOLINE).
  8. Disconnect Crankshaft Position (CKP) sensor. Attempt to start engine. Does engine start and continue to run? If yes, go to step  11. If no, go to next step.
  9. Inspect for the following:
    • A collapsed air intake duct.
    • A restricted air filter element.
    • Spark plugs for being gas or coolant fouled. If spark plugs are fouled, determine what caused condition.
    • An engine mechanical condition (worn timing chain, gears and low compression).
    • A restricted exhaust system.
    • Engine Coolant Temperature (ECT) sensor is not close to actual engine temperature. See DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE or DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article.
    • Compare MAP/BARO parameters to another vehicle. Parameters should be close in value. See DTC P0105: MAP SYSTEM PERFORMANCE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article.
    • TP sensor for being stuck in range. See DTC P1221: EXCESSIVE DIFFERENCE BETWEEN THROTTLE POSITION SENSORS under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article.

    After repairs, go to step  12.

  10. Repair Ignition 1 signal voltage circuit for an open or a short to ground. Replace fuse if necessary. After repairs, go to next step.
  11. Replace CKP sensor. After repairs, go to next step.
  12. Clear DTCs with scan tool. Turn OFF the ignition for 30 seconds. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step  2.
  13. Allow engine to reach operating temperature. Observe DTC information with scan tool. Are there any DTCs that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER XL article.
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