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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 530 (Charging System) >> Diagnostic Tests >> DTC P1634: Improper Ignition 1 Input >> Diagnostic Procedure

Diagnostic Procedure

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. If diagnostic system check was not performed, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK  under ON-VEHICLE TESTING. If diagnostic system check was performed, go to next step.
  2. If the engine runs with the ignition OFF, go to step  6 . If not, go to next step.
  3. If DTC's P0740, P0753, P0785, or P1860 are also set, see DIAGNOSTIC TROUBLE CODE DEFINITIONS under SELF-DIAGNOSTICS - 4.2L article or SELF-DIAGNOSTICS - 5.3L article in ENGINE PERFORMANCE. If not, go to next step.
  4. Turn ignition off. Disconnect the PCM. Connect a test light between the ignition 1 voltage circuit and a good ground. See WIRING DIAGRAMS  . Turn ignition on, with engine off. If the test light illuminates, go to step  7 . If not, go to next step.
  5. Test the ignition 1 voltage circuit for an open between the splice and the PCM. See WIRING DIAGRAMS  . If problem is detected, repair or replace as necessary. Then, go to step  9 .
  6. Disconnect the PCM. Test both ignition 1 voltage circuits for a short to voltage. See WIRING DIAGRAMS  . If problem is detected, repair or replace as necessary. Then, go to step  9 .
  7. Test for an intermittent and for poor connection at the PCM. If problem is detected, repair or replace as necessary. Then, go to step  9 . If not, go to next step.
  8. Replace PCM. See REMOVAL & INSTALLATION article in ENGINE PERFORMANCE. Reprogram PCM. 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  . If the DTC test passes, go to next step. If not, go to step  2 .
  10. Observe the Capture Info with a scan tool. If scan tool displays any DTC's that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS under SELF-DIAGNOSTICS - 4.2L article or SELF-DIAGNOSTICS - 5.3L article in ENGINE PERFORMANCE. If not, system is okay.
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