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HOMESERVICE MANUALSCHEVROLET1998CHEVY EXPRESS G2500, VAN PASSENGER EXTENDED, 5.0 MREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 19 (ENGINE CONTROLS - BASIC DIAGNOSTIC PROCEDURES - 5.7L (G SERIES))ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECKDLC DIAGNOSIS OR NO SCAN TOOL DATA
1998 Chevrolet Chevy Express G2500, Van Passenger Extended, 5.0 M

DLC Diagnosis Or No Scan Tool Data

1998 Chevrolet Chevy Express G2500, Van Passenger Extended, 5.0 MSECTION DLC Diagnosis Or No Scan Tool Data
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1997 GMC Savana Special, 1997 GMC Savana Camper Special, 1997 GMC Savana, 1997 Chevrolet RV Cutaway, and 1997 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  . After performing OBD system check, go to next step.
  2. Using a test light connected to ground, probe DLC battery feed circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
  3. Using a test light connected to battery voltage, probe DLC ground circuit. See the WIRING DIAGRAMS article. If test light illuminates on both circuits, go to next step. If test light does not illuminate on both circuits, go to step 12).
  4. Check cigarette lighter for power. If power is present at cigarette lighter, go to next step. If power is not present at cigarette lighter, go to step 13).
  5. Install and check scan tool operation on another vehicle. If scan tool operates, go to next step. If scan tool does not operate, go to step 14).
  6. Using DVOM connected to ground, measure voltage of DLC serial data line circuit. See the WIRING DIAGRAMS article. If voltage is less than 7 volts, go to next step. If voltage is more than 7 volts, go to step 16).
  7. Using DVOM connected to ground, again measure voltage of DLC serial data line circuit. If voltage is less than one volt, go to next step. If voltage is more than one volt, go to step 16).
  8. Turn ignition off. Using DVOM connected to ground, measure resistance of DLC serial data line circuit. If resistance is less than 10 milliohms, go to next step. If resistance is more than 10 milliohms, go to step 10).
  9. Disconnect VCM connectors. Using DVOM connected to ground, measure resistance of DLC serial data line circuit. If resistance is less than 10 milliohms, go to step 17). If resistance is more than 10 milliohms, go to step 15).
  10. Repair open in serial data line circuit. After repairs, go to step 18).
  11. Repair open in DLC battery feed circuit. After repairs, go to step 18).
  12. Repair open in circuit that did not cause test light to illuminate. After repairs, go to step 18).
  13. Repair cigarette lighter. After repairs, go to step 18).
  14. Repair or replace faulty scan tool and/or cables. After repairs, go to step 18).
  15. Repair short to ground in serial data line circuit. After repairs, go to step 18).
  16. Repair short to voltage in serial data line circuit. After repairs, go to step 18).
  17. Replace VCM. Reprogram replacement VCM. After replacing VCM, go to next step.
  18. Using scan tool, select DTC, CLEAR INFO function. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and dies/stalls, go to step 2).
  19. Warm engine to normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTC(s) are present, diagnose DTC. See the TESTS W/CODES article. If DTC(s) are not present, go to next step.
  20. Select CAPTURE INFO, REVIEW INFO function. If additional DTC(s) are displayed, diagnose DTC. See the TESTS W/CODES article. If DTC(s) are not present, system is okay.
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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.