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DTC U1040: Loss Of Class 2 Communication With Abs: Testing

WARNING: This page is about a different car, the 1999 Buick Regal and 1999 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  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  under SYSTEM TESTS.
  2. Turn ignition off. Disconnect scan tool. Disconnect negative battery cable. Disconnect splice pack SP205. See COMPONENT LOCATIONS  . Using DVOM, individually check resistance between SP205 terminal "A" and each terminal "B", "E", "G", "L", and "M". See WIRING DIAGRAMS  . See Figure . If resistance is less than 2 ohms at all terminals, go to next step. If resistance is greater than 2 ohms at all terminals, go to step  7 .
  3. Disconnect EBTCM Light Gray 24-pin connector C1. Using DVOM, check resistance between SP205 harness connector terminal "E" (Light Blue wire) and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step  8 .
  4. Turn ignition on. Using DVOM, check voltage between SP205 harness connector terminal "E" (Light Blue wire) and ground. If reading is less than 2 volts, go to next step. If reading is greater than 2 volts, go to step  9 .
  5. Using DVOM, check resistance between SP205 harness connector terminal "E" (Light Blue wire) and EBTCM harness connector C1 terminal A1 (Light Blue wire). If resistance is less than 2 ohms, go to next step. If resistance is greater than 2 ohms, go to step  10 .
  6. Turn ignition off. Reconnect EBTCM connector C1. Connect scan tool. Turn ignition on. Using scan tool, attempt to establish communication with EBTCM. If scan tool communicates with EBTCM, go to step  12 . If scan tool does not communicate with EBTCM, go to STEP  11 .
  7. Replace splice pack SP205. Go to step  13 .
  8. Repair short to ground in Light Blue wire between EBTCM connector C1 and splice pack SP205. Go to step  13 .
  9. Repair short to battery in Light Blue wire between EBTCM connector C1 and splice pack SP205. Go to step  13 .
  10. Repair poor connection or open in Light Blue wire between EBTCM connector C1 and splice pack SP205. Go to step  13 .
  11. Class 2 serial data line is okay, but EBTCM is not communicating class 2 data because of internal malfunction. Go to appropriate ANTI-LOCK BRAKES article in BRAKES to diagnose and repair problem.
  12. System is operating properly at this time. See DIAGNOSTIC AIDS  . After any repairs are made, go to next step.
  13. Turn ignition off. Reinstall all components and connectors. Turn ignition on. Using scan tool, clear DTCs. Check for DTCs. If any DTCs are current, perform BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS. If no DTCs are current, system is operating properly.
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