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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. After performing diagnostic system check, go to next step.
  2. Using scan tool, check for DTCs. If DTCs P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631 or P1683 are set, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If DTCs are not set, go to next step.
  3. Does scan tool display any Body Control Module (BCM) or Vehicle Theft Deterrent (VTD) DTCs? If yes, diagnose affected DTCs. See appropriate BODY CONTROL MODULES or ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  4. Using a test light connected to ground, probe both sides of the following fuses: ECM 1, INJ "A" and INJ "B". Does the test light illuminate on at least one side of all of the fuses? If yes, go to next step. If no, go to IGNITION RELAY under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - 4.3L SIERRA & SILVERADO article.
  5. Attempt to start engine. Observe Engine Speed parameter with a scan tool, while engine is cranking. Does engine speed increment? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM  under IGNITION SYSTEMS.
  6. Monitor ignition 1 signal voltage parameter with a scan tool. See Figure . Is ignition 1 signal voltage parameter at battery voltage? If yes, go to next step. If no, go to step  11 .
  7. Command fuel pump on with a scan tool. Does fuel pump turn on? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.3L SIERRA & SILVERADO article.
  8. Turn ignition off. Disconnect a spark plug wire. Install Spark Tester (J-26792) to spark plug wire. Attempt to start engine. Does spark tester spark? If yes, go to next step. If no, go to DISTRIBUTOR IGNITION SYSTEM  under IGNITION SYSTEMS.
  9. Turn ignition off. Install Fuel Pressure Gauge (J-34730-1A). Turn ignition on, with engine off. Command fuel pump on with a scan tool. Is fuel pressure within 55-62 psi (379-427 kPa ) while fuel pump is operating? If yes, go to next step. If no, go to FUEL SYSTEMS  .
  10. Inspect for collapsed air intake duct, restricted air filter element, fouled spark plugs, engine mechanical problem or restricted exhaust system. Check if ECT sensor is NOT close to actual engine temperature. Compare MAP/BARO parameters to another vehicle. The parameters should be close in value. Check if TP sensor is stuck in range. Repair as necessary. After repairs, go to step  14 .
  11. Test ignition 1 signal voltage circuit for an open or for a short to ground. See Figure . Replace fuse, if necessary. Did you find and correct condition? If yes, go to step  14 . If no, go to next step.
  12. Inspect for poor connections at harness connector of PCM. Did you find and correct condition? If yes, go to step  14 . If no, go to next step.
  13. Replace PCM. See appropriate REMOVAL & INSTALLATION article. After replacing PCM, go to next step.
  14. Clear DTCs with a scan tool. Turn ignition off 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 .
  15. Observe Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If no DTCs are set, system okay.
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