LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 2001 >> Catera >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Body Control Modules >> Diagnostic Tests >> DTC U2103: Fewer Controllers On Bus Than Programmed >> Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC U2103: Fewer Controllers On Bus Than Programmed: Testing

  1. Perform appropriate diagnostic system check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE for ECM, appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS for TCM and appropriate ANTI-LOCK/TCS - CATERA article in BRAKES for EBCM. After performing diagnostic system check, go to next step.
  2. Install a scan tool. Turn ignition on, with engine off. Using scan tool, monitor DTC INFORMATION for DTC U2100 and for DTCs in U2105-U2108 range. If scan tool indicates that DTC U2100 or DTCs in U2105-U2108 range are either current or history DTCs, perform diagnostic test for DTC. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If DTC U2100 or DTCs in U2105-U2108 range are not current or history DTCs, go to next step.
  3. Using scan tool, select data display for ECM, EBCM and TCM. Observe data parameters listed in DIAGNOSTIC AIDS  for missing or mismatched data. If data is missing or there is a mismatch between data sent and data received indicating a malfunction, go to next step. If all modules are receiving data properly, go to step  6 .
  4. Check electrical harness connector from suspect control module for poor or loose connections. See PRELIMINARY INSPECTION  under TROUBLE SHOOTING. If malfunction is located and repaired, go to step  9 . If malfunction is not located and repaired, go to next step.
  5. Replace and program suspect module(s) not communicating data on CAN bus circuit. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE for ECM, appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS for TCM and appropriate ANTI-LOCK/TCS - CATERA article in BRAKES for EBCM. After replacement, go to next step.
  6. Using scan tool, clear DTCs. Turn ignition off. Wait at least 10 seconds. Turn ignition on, with engine off. Check for DTCs from ECM, EBCM and TCM. If any DTCs reset, go to next step. If no DTCs reset, system okay.
  7. Disconnect electrical harness connector(s) from suspect module(s) that are not communicating data on CAN bus circuit. Inspect harness connector(s) for poor terminal contact, corrosion and damage. See PRELIMINARY INSPECTION  under TROUBLE SHOOTING. If malfunction is located and repaired, go to step  9 . If malfunction is not located and repaired, go to next step.
  8. Replace suspect module(s) that set a DTC. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE for ECM, appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS for TCM and appropriate ANTI-LOCK/TCS - CATERA article in BRAKES for EBCM. After replacement, go to next step.
  9. Using scan tool, clear DTCs. Turn ignition off. Wait at least 10 seconds. Turn ignition on, with engine off. Retrieve DTCs from ECM, EBCM and TCM. If any DTCs reset, go to step  2 . If no DTCs reset, system is okay.
scientia non olet · About LEMON Manuals