LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 1997 >> Century Custom >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Module >> Diagnosis & Repair >> DTC U1040, EBTCM Class 2 Source Id 28 >> Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC U1040, EBTCM Class 2 Source Id 28: Testing

  1. If BCM diagnostic system check was performed, go to next step. If BCM diagnostic system check was not performed, go to BCM DIAGNOSTIC SYSTEM CHECK  .
  2. If SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DATA LINE  test has already been performed, go to next step. If SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DATA LINE test has not been performed, go to step 4).
  3. Turn ignition on. Clear DTCs. Wait for 10 seconds and check for DTCs. If DTC U1040 sets again, go to next step. If DTC U1040 does not set again, system is operating properly.
  4. Turn ignition off. Connect scan tool. Turn ignition on. Using scan tool, attempt to establish communication with EBTCM. If scan tool communicates with EBTCM, go to next step. If scan tool does not communicate with EBTCM, go to step 6).
  5. Check for poor connection at EBTCM connector C1 terminal A1 (Light Blue wire). EBTCM is located below instrument panel, to left of steering column. If connection is okay, go to step 7). If connection is not okay, go to step 8).
  6. Ensure splice pack SP205 is seated properly. Splice pack SP205 is located below instrument panel, by right side of steering column. If splice pack SP205 is seated properly, go to step 9). If splice pack SP205 is not seated properly, go to step 10).
  7. Check for poor connection at BCM 24-pin connector C2 terminal B5 (Light Green wire). If connection is okay, go to step 11). If connection is not okay, go to step 12).
  8. Repair poor connection at EBTCM connector C1 terminal A1 (Light Blue wire). Go to step 13).
  9. Using DVOM, check continuity between EBTCM connector C1 terminal A1 (Light Blue wire) and BCM connector C2 terminal B5 (Light Green wire). If continuity exists, problem exists in PCM system. See appropriate TESTS W/O CODES article in ENGINE PERFORMANCE section. If continuity does not exist, go to step 14).
  10. Seat splice pack SP205 properly. Using scan tool, attempt to establish communication with EBTCM. If scan tool communicates with EBTCM, system is operating properly. If scan tool does not communicate with EBTCM, go to step 14).
  11. Check for poor connections at splice pack SP205 terminals "A" (Purple wire), "E" (Light Blue wire) and "M" (Light Green wire). If connections are okay, system is operating properly. If connections are not okay, go to step 15).
  12. Repair poor connection at BCM connector C2 terminal B5 (Light Green wire). Go to next step.
  13. Turn ignition off. Reinstall all components and connectors. Turn ignition on. Using scan tool, clear DTCs. Perform BCM DIAGNOSTIC SYSTEM CHECK  .
  14. Using DVOM, check continuity of Light Blue wire between EBTCM connector C1 terminal A1 and splice pack SP205. If continuity exists, go to step 16). If continuity does not exist, go to step 17).
  15. Repair poor connection(s) at splice pack SP205. Go to step 13).
  16. Replace splice pack SP205. Go to step 13).
  17. Repair poor connection or open in Light Blue wire between EBTCM connector C1 and splice pack SP205. Go to step 13).
scientia non olet · About LEMON Manuals