LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Chevrolet >> 2000 >> Venture Plus >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Tests >> Fuel System (CNG) >> AF Fuel Pump Relay
April 5, 2026: LEMON Manuals is launched! Read the announcement.

AF Fuel Pump Relay

  1. Perform OBD system check. See ON BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. Go to next step.
  2. Ensure both fuel systems are at least 1/4 full. Install CNG fuse (20-amp), if removed. Try to start engine. If engine does not start, go to next step. If engine starts, go to step  4.
  3. Turn ignition off for 30 seconds. Disconnect 2-pin fuel pump connector C019. Connect test light between fuel pump harness connector terminal "A" (Gray wire) and ground. Turn ignition on. If test light illuminates for 2 seconds, go to step  14. If test light did not illuminate for 2 seconds, go to step  13.
  4. If vehicle operates on CNG, but not on gasoline, go to next step. If vehicle operates on both fuels, check CNG system. See ON BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
  5. Turn ignition off for 30 seconds. Using test light connected to ground, backprobe AF fuel pump relay terminal No. 30 (Gray wire). Turn ignition on. If test light illuminates for 2 seconds, go to next step. If test light does not illuminate, go to step  15.
  6. Start engine. Ensure vehicle is operating on CNG. Using test light connected to ground, backprobe AF fuel pump relay terminal No. 87A (Gray/Black wire). If test light does not illuminate, go to next step. If test light illuminates, go to step  8.
  7. Monitor test light while turning ignition off. If light stays on for 2 seconds after ignition is turned off, go to step  10. If light does not stay on for 2 seconds after ignition is turned off, go to step  16.
  8. Start engine. Using test light connected to battery voltage, backprobe AF fuel pump relay terminal No. 86 (Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step  17.
  9. Using test light connected to ground, backprobe AF fuel pump relay terminal No. 85 (Brown wire). If test light illuminates, go to step  20. If test light does not illuminate, go to step  18.
  10. Turn ignition off. Remove CNG fuse (20-amp) from underhood fuse block to force gasoline operation. Attempt to start engine. If engine does not operate on gasoline, go to next step. If engine operates on gasoline, check CNG operation. See ON BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
  11. Turn ignition off for 30 seconds. Disconnect 2-pin fuel pump connector C019. Connect a fused jumper wire between harness connector terminals. Attempt to start engine. If engine does not operate on gasoline, go to next step. If engine operates on gasoline, go to step  19.
  12. Repair problem in gasoline fuel delivery system. Check gasoline fuel pump, power circuit and ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22.
  13. Repair problem in gasoline fuel pump relay circuit. Check gasoline fuel pump relay, fuse, control circuit, power circuit and ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22.
  14. Check for open or poor contact on fuel pump power circuit (Gray wire) between fuel pump harness connector C019 terminal "A" and splice. See WIRING DIAGRAMS article. If no problem is found, diagnose no start condition. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If any problem is found, repair as necessary. After repairs, go to step  22.
  15. Repair open on Gray wire between AF fuel pump relay terminal No. 30 and splice. See WIRING DIAGRAMS article. After repairs, go to step  22.
  16. Check AF fuel pump relay terminal contact. Check for short to battery voltage on control circuit (Brown wire). If no problem is found, go to step  20. If any problem is found, repair as necessary. After repairs, go to step  22.
  17. Repair open circuit on Black wire between AF fuel pump relay terminal No. 86 and splice. See WIRING DIAGRAMS article. After repairs, go to step  22.
  18. Check for poor contact, open or short to ground on Brown wire between AF ECU connector C001 terminal No. 30 and AF fuel pump relay terminal No. 85. If no problem is found, go to step  21. If any problem is found, repair as necessary. After repairs, go to step  22.
  19. Repair open circuit on Gray/Black wire between AF fuel pump relay terminal No. 87A and fuel pump connector C019 terminal "B". After repairs, go to step  22.
  20. Replace AF fuel pump relay. After repairs, go to step  22.
  21. Replace AF ECU. Program new AF ECU. After repairs, go to step  22.
  22. Reconnect all components and connectors. Using scan tool, clear all DTCs. Turn ignition off for 30 seconds. Start engine. Test drive vehicle. If no problems are found, MIL operates properly and no DTCs are set, test is complete. If any problems are found, MIL does not operate properly or DTCs are set, perform OBD system check. See ON BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
scientia non olet · About LEMON Manuals