Diagnostic Procedures

2000 Chevrolet Chevy Express G3500, Van Cargo, 4.3 WSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Clear DTCs. Using Connector Test Kit (J-35616-A), backprobe signal and ground circuits of VSS connector. Raise vehicle wheels and place engine in operating gear. Check voltage with voltmeter on 200-volt AC scale. If voltage reading is constant, go to step  5. If voltage reading is not constant, go to next step.
  3. If voltage varies, see DIAGNOSTIC AIDS . If voltage does not vary, go to next step.
  4. If voltmeter indicates no voltage, go to step  11. If voltmeter does not indicate no voltage, go to step  12.
  5. Turn ignition off. Disconnect VSS connector. With vehicle still raised, engine operating, transmission in gear and voltmeter on 200-volt AC scale, check voltage between VSS connector terminals. If voltage varies with RPM, go to step  7. If voltage does not vary with RPM, go to next step.
  6. Replace VSS. After replacing sensor, go to step  12.
  7. Check for poor connections at VCM and VSS. If a problem is found, go to step  9. If no problem is found, go to next step.
  8. Check for open or short in VSS signal and ground circuits. If a problem is found, go to step  10. If no problem is found, go to step  12.
  9. Repair connections. After repairs, go to step  12.
  10. Repair open or short. After repairs, go to step  12.
  11. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step  2.
  13. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.