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Control Module Communication

  1. Connect scan tool to DLC connector. Turn ignition switch to ON position. Verify that scan tool turns on. If scan tool turns on, go to next step. If scan tool does not turn on, go to step  5 .
  2. Attempt to communicate with ABS control module. If scan tool will communicate with ABS control module, go to next step. If scan tool cannot communicate with ABS control module, go to step  8 .
  3. Remove key from ignition switch lock cylinder. Attempt to lock/unlock vehicle with key. If vehicle will lock/unlock with key, go to next step. If vehicle will not lock/unlock with key, go to step  6 .
  4. Check for open in White wire between VGLA control module connector terminal B-19 and DLC connector terminal No. 7. Refer to WIRING DIAGRAMS  . Repair as necessary. Go to step  14 .
  5. Check power and ground feed circuits using scan tool according to manufacturer's instructions. See POWER DISTRIBUTION section in SYSTEM WIRING DIAGRAMS article. After repairs, go to step  14 .
  6. Check VGLA connector for loose or corroded terminals. Repair as necessary. Turn ignition switch to ON position. Attempt to communicate with VGLA control module. If scan tool will communicate with VGLA control module, symptom has been repaired. If scan tool cannot communicate with VGLA control module, go to next step.
  7. Turn ignition switch to OFF position. Disconnect VGLA control module. Check fuse No. 6 (50-amp) in relay/main fuse box in engine compartment. If fuse is blown, check Green/Red wire for short to ground between VGLA control module connector terminal B-1 and fuse No. 6. See WIRING DIAGRAMS  . If fuse is okay, use DVOM to measure voltage between ground and VGLA control module connector B-1. Battery voltage should be indicated. If battery voltage is indicated, go to step  14 . If battery voltage is not indicated, check for open in Red wire before fuse No. 6 or open in Green/Red wire between VGLA control module connector terminal B-1 and fuse No. 6. Repair as necessary. Go to step  14 .
  8. Turn ignition switch to OFF position. Disconnect VGLA control module. Disconnect scan tool. Use DVOM to measure resistance between VGLA connector terminal B-1 and DLC terminal No. 7 (White wire). See WIRING DIAGRAMS  . If continuity is indicated, go to next step. If continuity is not indicated, go to step  4 .
  9. Turn ignition switch to OFF position. Connect VGLA control module. Use DVOM to measure voltage between ground and DLC terminal No. 7 (White wire). Turn ignition switch to ON position. If reading is 9 to 11 volts, go to step  12 . If reading is less than 9 volts, go to next step. If reading is greater than 11 volts, go to step  11 .
  10. Check for short to ground in White wire between VGLA control module connector terminal B-19 and DLC connector terminal No. 7. See WIRING DIAGRAMS  . Repair as necessary. Go to step  14 .
  11. Check for short to battery voltage in White wire between associated control modules and DLC connector terminal No. 7. See DATA LINK CONNECTORS section in SYSTEM WIRING DIAGRAMS article. Repair as necessary. Go to step  14 .
  12. Turn ignition switch to ON position. Attempt to communicate with VGLA control module. If scan tool will communicate with VGLA control module, go to next step. If scan tool cannot communicate with VGLA control module, go to step  5 .
  13. Check VGLA and DLC connectors for loose or corroded terminals. Repair as necessary. Go to next step.
  14. Turn ignition switch to OFF position. Reconnect all disconnected components. Turn ignition switch to ON position. Attempt to communicate with VGLA control module. If scan tool will communicate with VGLA control module, symptom has been repaired. If scan tool cannot communicate with VGLA control module, fault is still present.
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