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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 370 (Engine Control System - Self-Diagnostics - 4.2L) >> Diagnostic Tests >> DTC P1633: Ignition 0 Circuit Performance >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Does the engine run with the ignition OFF? If yes, go to step  6. If no, go to next step.
  3. Are DTCs P0740, P0753, P0785, or P1860 also set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Turn ignition off. Disconnect the PCM. Connect a test light between the ignition 0 voltage circuit and a good ground. Turn ignition on, with engine off. Does the test light illuminate? If yes, go to step  9. If no, go to next step.
  5. Test the ignition 0 voltage circuit for an open between the splice and the PCM. Did you find and correct the condition? If yes, go to step  9. If no, go to next step.
  6. Disconnect the PCM. Test both ignition 1 voltage circuits for a short to voltage. Did you find and correct the condition? If yes, go to step  9. If no, go to next step.
  7. Test for an intermittent and for poor connection at the PCM. Did you find and correct the condition? If yes, go to step  9. If no, go to next step.
  8. Replace PCM. See REMOVAL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  9. Clear the DTCs with scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions For Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  10. Observe the stored information, Capture Info with scan tool. Does scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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