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Scan Tool Does Not Communicate With Class 2 Device

CAUTION: BCM Brown 24-pin connector C1 contains power and ground sources. When removing BCM, always disconnect connector C1 first before disconnecting connectors C2 and C3. When installing BCM, always reconnect connectors C2 and C3 first, then connector C1 last.
  1. Install scan tool. If scan tool works, go to next step. If scan tool does not work, go to SCAN TOOL INOPERATIVE  .
  2. Turn ignition on. Attempt to communicate with all control modules on class 2 serial data circuit. If any module communicates with scan tool, go to next step. If no module communicates with scan tool, go to step  5 .
  3. Check DTCs for each module. Record each DTC, status (history or current) and which module set the DTC. If any communication DTCs (DTCs with "U" prefix) exist, go to next step. If no communication DTCs exist, check for intermittent or poor connections.
  4. For diagnosis and repair of "U" prefix DTCs, go to appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  table.
  5. Turn ignition off. Disconnect scan tool from DLC. Check DLC terminals No. 2 (Purple wire) and No. 5 (Black/White wire) for proper contact. If no problem is found, go to next step. If any looseness or damage exists, repair as necessary. After repairs, go to step  21 .
  6. Check for open circuit between DLC terminal No. 5 (Black/White wire) and ground. If no problem is found, go to next step. If problem is found, repair open or high resistance between DLC and ground. After repairs, go to step  21 .
  7. Disconnect Black 12-pin splice pack SP201 connector (located below instrument panel fuse block, taped to body harness). Check for corrosion and damage of terminals. If no problem is found, go to next step. If any looseness or damage exists, repair as necessary. After repairs, go to step  21 .
  8. Check for open or short on Purple wire between DLC terminal No. 2 and splice pack SP201 harness connector C1 terminal "A". See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If no problem is found, go to next step. If problem is found, repair open or short. After repairs, go to step  21 .
  9. Connect a jumper wire between splice pack SP201 connector terminals "A" (Purple wire) and "M" (Light Green wire). Turn ignition on. Attempt to communicate with BCM. If BCM will not communicate, go to next step. If BCM communicates, go to step  11 .
  10. Turn ignition off. Disconnect BCM connectors. Check for short to ground or short to power (ignition on) on Light Green wire between BCM connector C1, terminal A12 and splice pack SP201 terminal "M". See Fig 1 . If no problem is found, go to step  19 . If problem is found, repair as necessary. After repairs, go to step  21 .
  11. Leave jumper wire from step  9 connected. Connect another jumper wire between splice pack SP201 connector terminals "A" (Purple wire) and "B" (Dark Green wire). See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Turn ignition on. Attempt to communicate with PCM. If PCM will not communicate, go to next step. If BCM communicates, go to step  13 .
  12. Turn ignition off. Disconnect PCM connectors. Check for short to ground or short to power (ignition on) on Dark Green wire between PCM connector C4 terminal No. 11 and splice pack SP201 terminal "B". If no problem is found, go to step  19 . If problem is found, repair as necessary. After repairs, go to step  21 .
  13. Leave jumper wire from step  9 connected. Remove jumper wire from splice pack SP201 connector terminal "D". Connect jumper wire between splice pack SP201 connector terminals "A" (Purple wire) and "E" (Light Blue wire). See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Turn ignition on. Attempt to communicate with Electronic Brake Control Module (EBCM). If EBCM will not communicate, go to next step. If EBCM communicates, go to step  15 .
  14. Turn ignition off. Disconnect EBCM connectors. Check for short to ground or short to power (ignition on) on Light Blue wire between EBCM connector C1, terminal B6 (325 ABS) or C9 (310 ABS) and splice pack SP201 terminal "E". If no problem is found, go to step  19 . If problem is found, repair as necessary. After repairs, go to step  21 .
  15. Leave jumper wire from step  9 connected. Remove jumper wire from splice pack SP201 connector terminal "E". Connect jumper wire between splice pack SP201 connector terminals "A" (Purple wire) and "F" (Dark Blue wire). Turn ignition on. Attempt to communicate with inflatable restraint Sensing and Diagnostic Module (SDM). If SDM will not communicate, go to next step. If SDM communicates, go to step  17 .
  16. Turn ignition off. Disconnect SDM connector. Check for short to ground or short to power (ignition on) on Dark Blue wire between SDM connector terminal A4 and splice pack SP201 terminal "F". See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If no problem is found, go to step  19 . If problem is found, repair as necessary. After repairs, go to step  21 .
  17. Leave jumper wire from step  9 connected. Remove jumper wire from splice pack SP201 connector terminal "F". Connect jumper wire between splice pack SP201 connector terminals "A" (Purple wire) and "G" (Gray wire). Turn ignition on. Attempt to communicate with instrument cluster. If instrument cluster will not communicate, go to next step. If instrument cluster communicates, go to step  21 .
  18. Turn ignition off. Disconnect instrument cluster connector. Check for short to ground or short to power (ignition on) on Gray wire between instrument cluster connector terminal A6 and splice pack SP201 terminal "G". If no problem is found, go to next step. If problem is found, repair as necessary. After repairs, go to step  21 .
  19. Check terminals of connector and module that is not communicating. If no problem is found, go to next step. If problem is found, repair as necessary. After repairs, go to step  21 .
  20. Replace module that is not communicating. See appropriate article for replacement and programming information. After repairs, go to next step.
  21. Reconnect all components and connectors. Connect scan tool. Turn ignition on. If scan tool does not communicate, disconnect scan tool, then reconnect to reset communication. Check DTCs for each module. Record each DTC, status (history or current) and which module set the DTC. If any DTCs exist, go to next step. If no DTCs exist, go to step  23 .
  22. Diagnose and repair any DTCs as necessary. See appropriate article for test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  table. After all repairs are complete, go to next step.
  23. Using scan tool, clear all DTCs.
Fig 1: Identifying BCM Connector C1 Terminals
G99B02306Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying BCM Connector C2 Terminals
G99F02308Courtesy of GENERAL MOTORS CORP.
Fig 3: Identifying BCM Connector C3 Terminals
G99D02307Courtesy of GENERAL MOTORS CORP.
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