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Home >> Oldsmobile >> 1999 >> Intrigue GL, 3.5 H >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 2 (Anti-Lock Brake System With Traction Control System - Abs-VI) >> Diagnostic Tests >> DTC U1255: Class 2 Communications Malfunction (1998 Century, Intrigue & Regal)

DTC U1255: Class 2 Communications Malfunction (1998 Century, Intrigue & Regal)

WARNING: This page is about a different variant/trim than selected.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
  2. Using scan tool, attempt to establish communication with same system on a different vehicle. If communication can be established, go to next step. If communication cannot be established, see scan tool operation manual for scan tool diagnosis.
  3. Turn ignition off. Check Data Link Connector (DLC) for poor terminal contact, corrosion or damage. If connector is faulty, go to step 14)  . If connector is okay, go to next step.
  4. Turn ignition on, with engine off. Install scan tool. Using scan tool, attempt to establish communication with other modules connected to serial data line. If communication can be established, go to step 12)  . If communication cannot be established, go to next step.
  5. Turn ignition off. Disconnect instrument cluster, heater-A/C control, Body Control Module (BCM), and Powertrain Control Module (PCM). Disconnect 24-pin EBCM/EBTCM connector C1 and 8-pin EBCM/EBTCM connector C2. See EBCM/EBTCM LOCATION  under REMOVAL & INSTALLATION. Using DVOM, measure resistance between terminals No. 2 (Purple wire) and 4 (Black wire) of DLC. If resistance is infinite, go to next step. If resistance is not infinite, go to step 15)  .
  6. Turn ignition on, with engine off. Using DVOM, measure voltage between terminals No. 2 (Purple wire) and 4 (Black wire) of DLC. If voltage is not present, go to next step. If voltage is present, go to step 16)  .
  7. Turn ignition off. Reconnect instrument cluster. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with instrument cluster. If communication can be established, go to next step. If communication cannot be established, go to appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
  8. Turn ignition off. Reconnect heater-A/C control. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with heater-A/C control. If communication can be established, go to next step. If communication cannot be established, see appropriate AIR CONDITIONING & HEATING SERVICE & REPAIR article.
  9. Turn ignition off. Reconnect BCM. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with BCM. If communication can be established, go to next step. If communication cannot be established, go to appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  10. Turn ignition off. Reconnect PCM. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with PCM. If communication can be established, go to next step. If communication cannot be established, go to step 19)  .
  11. Turn ignition off. Reconnect EBCM/EBTCM connectors C1 and C2. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with EBCM/EBTCM. If communication can be established, go to step 20)  . If communication cannot be established, go to step 18)  .
  12. Turn ignition off. Disconnect 24-pin EBCM/EBTCM connector C1. Check EBCM/EBTCM connector C1 for poor terminal contact, corrosion or damage. If connector is faulty, go to step 14)  . If connector is okay, go to next step.
  13. Using DVOM, measure resistance between terminal No. 2 (Purple wire) of DLC and terminal A1 (Light Blue wire) of EBCM/EBTCM connector C1. If resistance is 0-2 ohms, go to step 18)  . If resistance is not 0-2 ohms, go to step 17)  .
  14. Replace all faulty terminals or connectors.
  15. Repair short to ground in DLC Purple wire or Light Blue wire circuit.
  16. Repair short to voltage in DLC Purple wire or Light Blue wire circuit.
  17. Repair open in Purple wire or Light Blue wire between DLC and EBCM/EBTCM.
  18. Replace EBCM/EBTCM. See ELECTRONIC BRAKE CONTROL MODULE/ ELECTRONIC BRAKE & TRACTION CONTROL MODULE (EBCM/EBTCM)  under REMOVAL & INSTALLATION.
  19. Perform PCM ON-BOARD DIAGNOSTIC SYSTEM CHECK. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  20. Malfunction is not currently present. When DTC U1255 is current (malfunction in Purple wire or Light Blue wire circuit), no communication can be established with scan tool. When malfunction is present, DTC U1255 will be stored in system memory. Before performing diagnostic testing for DTC U1255, perform PCM on-board diagnostic system check to eliminate possible faulty PCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside insulation. Frequency of malfunction can be determined by using enhanced diagnostic function of scan tool. Check for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wiring connections, or damaged wiring harness.

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