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Scan Tool Does Not Communicate With Class 2 Device

NOTE: To identify wire colors and modules on serial data links, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.
  1. Ensure battery condition, cold cranking amperage and reserve capacity meet specifications. Replace as necessary. Install scan tool to Data Link Connector (DLC). If scan tool powers up, go to next step. If scan tool does not power up, go to SCAN TOOL DOES NOT POWER UP  .
    Fig 1: Locating Data Link Connector (DLC) & Splice Pack SP205
    G00015136Courtesy of GENERAL MOTORS CORP.
  2. Turn ignition on, engine off. Try to establish scan tool communication with each module on class 2 device. (On Tech II scan tools, CLASS 2 MESSAGE MONITOR feature). If communication with any module is established, go to next step. If communication with any module is not established, go to step  5 .
  3. Select display DTC function for each module on class 2 device. Record all displayed DTCs, status of displayed DTCs and module that set DTC. If any DTCs in range of U1000 to U1255 are displayed, go to next step. If no DTCs in range of U1000 to U1255 are displayed, attempt to diagnose malfunctioning system or device by symptom. Go to appropriate article for malfunctioning system or device.
  4. If DTC U1000 is only DTC displayed, go to DTC U1000 & DTC U1255: CLASS 2 COMMUNICATION MALFUNCTION  under DIAGNOSTIC TESTS. If DTC U1000 is not only DTC displayed, go to DTC U1001-U1254: LOSS OF XXX COMMUNICATIONS  under DIAGNOSTIC TESTS.
  5. Turn ignition off. Disconnect scan tool from DLC. Inspect DLC terminal No. 2 (Purple wire) and terminal No. 5 (Black wire) for poor connections. If connections are okay, perform diagnostic system check for malfunctioning system or device. If fault was not located and repaired, go to next step.
  6. Using a DVOM, test DLC ground circuit terminal No. 5 (Black wire) for an open. See WIRING DIAGRAMS  . If circuit is okay, perform diagnostic system check for malfunctioning system or device. If fault was not located and repaired, go to next step.
  7. Disconnect splice pack SP205 located below instrument panel to right of steering column and inspect for poor connections. See Fig 1 . If connections are okay, perform diagnostic system check for malfunctioning system or device. If fault was not located and repaired, go to next step.
  8. Using a DVOM, test class 2 device circuit for an open or short between DLC connector terminal No. 2 (Purple wire) and splice pack SP205 terminal "A". See Fig 2 . If circuit is okay, perform diagnostic system check for malfunctioning system or device. If fault was not located and repaired, go to next step.
    Fig 2: Identifying Splice Pack SP205 Connector Terminals
    G98G00444Courtesy of GENERAL MOTORS CORP.
  9. Using correct terminal adapters from Connector Test Adapter Kit (J 35616-A), connect a jumper wire between splice pack SP205 connector terminal "A" (Purple wire) and terminal "M" (Light Green wire). Turn ignition on, with engine off. Using a scan tool connected to DLC, attempt to communicate with BCM. If scan tool communicates with BCM, go to step  11 . If scan tool does not communicate with BCM, go to next step.
  10. Turn ignition off. Disconnect BCM harness connector. Using a DVOM, test class 2 device circuit (Light Green wire) for a short to voltage (ignition on) or short to ground (ignition off) between splice pack SP205 connector terminal "M" and Purple BCM connector C2 terminal A8. Repair circuit as necessary. If circuit is okay, go to step  23 . If fault was not located and repaired, go to step  21 .
    Fig 3: Identifying BCM Connectors & Terminals
    G00015134Courtesy of GENERAL MOTORS CORP.
  11. Leave jumper wire connected between splice pack SP205 connector terminal "A" (Purple wire) and terminal "M" (Light Green wire). Connect another jumper wire from connector test adapter kit between jumper connected to terminal "A" (Purple wire) of splice pack SP205 connector and terminal "B" (Dark Green wire) of splice pack SP205 connector. Turn ignition on, engine off. Using a scan tool connected to DLC, attempt to communicate with PCM. If scan tool communicates with PCM, go to step  13 . If scan tool does not communicate with PCM, go to next step.
  12. Turn ignition off. Disconnect Blue PCM harness connector C1. Using a DVOM, test class 2 device circuit (Dark Green wire) for a short to voltage (ignition on) or short to ground (ignition off) between splice pack SP205 connector terminal "B" and Blue PCM connector C1 terminal No. 58. Repair circuit as necessary. If circuit is okay, go to step  23 . If fault was not located and repaired, go to step  21 .
  13. Disconnect jumper wire from splice pack SP205 connector terminal "B" (Dark Green wire) and connect it to terminal "E" (Light Blue wire) of splice pack SP205 connector. Turn ignition on, engine off. Using a scan tool connected to DLC, attempt to communicate with EBCM. If scan tool communicates with EBCM, go to step  15 . If scan tool does not communicate with EBCM, go to next step.
  14. Turn ignition off. Disconnect EBCM harness connector. Using a DVOM, test class 2 device circuit (Light Blue wire) for a short to voltage (ignition on) or short to ground (ignition off) between splice pack SP205 connector terminal "E" and EBCM connector terminal B7. Repair circuit as necessary. If circuit is okay, go to step  23 . If fault was not located and repaired, go to step  21 .
  15. Disconnect jumper wire from splice pack SP205 connector terminal "E" (Light Blue wire) and connect it to terminal "F" (Dark Blue wire) of splice pack SP205 connector. Turn ignition on, engine off. Using a scan tool connected to DLC, attempt to communicate with SDM. If scan tool communicates with SDM, go to step  17 . If scan tool does not communicate with SDM, go to next step.
  16. Turn ignition off. Disconnect SDM harness connector. Using a DVOM, test class 2 device circuit (Dark Blue wire) for a short to voltage (ignition on) or short to ground (ignition off) between splice pack SP205 connector terminal "F and SDM connector terminal A5. Repair circuit as necessary. If circuit is okay, go to step  23 . If fault was not located and repaired, go to step  21 .
  17. Disconnect jumper wire from splice pack SP205 connector terminal "F" (Dark Blue wire) and connect it to terminal "G" (Gray wire) of splice pack SP205 connector. Turn ignition on, engine off. Using a scan tool connected to DLC, attempt to communicate with IPC. If scan tool communicates with IPC, go to step  19 . If scan tool does not communicate with IPC, go to next step.
  18. Turn ignition off. Disconnect IPC harness connector. Using a DVOM, test class 2 device circuit (Gray wire) for a short to voltage (ignition on) or short to ground (ignition off) between splice pack SP205 connector terminal "G" and IPC connector terminal B2. Repair circuit as necessary. If circuit is okay, go to step  23 . If fault was not located and repaired, go to next step.
  19. Disconnect jumper wire from splice pack SP205 connector terminal "G" (Gray wire) and connect it to terminal "L" (White wire) of splice pack SP205 connector. Turn ignition on, engine off. Using a scan tool connected to DLC, attempt to communicate with heater-A/C control. If scan tool communicates with heater-A/C control, go to step  23 . If scan tool does not communicate with heater-A/C control, go to next step.
  20. Turn ignition off. Disconnect heater-A/C control harness connector. Using a DVOM, test class 2 device circuit (White wire) for a short to voltage (ignition on) or short to ground (ignition off) between splice pack SP205 connector terminal "L" and heater-A/C control connector terminal D12. Repair circuit as necessary. If circuit is okay, go to step  23 . If fault was not located and repaired, go to next step.
  21. Inspect for poor connections of class 2 device circuit at applicable connector for module not communicating with scan tool. If connections are okay, go to step  23 . If fault was not located and repaired, go to next step.
  22. Replace module not communicating with scan tool. See REMOVAL & INSTALLATION  . After repair, go to next step.
  23. Turn ignition off. Remove all jumper wires and reconnect all disconnected connectors, splice pack SP205 and modules. Install scan tool to DLC. Turn ignition on, with engine off. Wait 10 seconds in case scan tool must reset due to a short on class 2 device circuit. Turn off or disconnect scan tool before proceeding. Reinstall or turn scan tool on and select display DTCs function for each module on class 2 device. Record all displayed DTCs, status of displayed DTCs and module that set DTC. If any DTCs that begin with "U" are displayed as CURRENT, go to step  25 . If no DTCs that begin with "U" are displayed as CURRENT, go to next step.
  24. If any DTCs were recorded that did not begin with "U", go to next step. If DTCs were recorded that did begin with "U", go to step  27 .
  25. Diagnose and repair recorded DTCs. Perform appropriate diagnostic procedure. See BODY CONTROL MODULE (BCM) DTC DEFINITIONS  table. For DTCs not listed, go to appropriate article for malfunctioning system or module. After repair, go to next step.
  26. If all DTCs have been diagnosed, go to next step. If all DTCs have not been diagnosed, repeat step  25 .
  27. Use scan tool to clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  . Test is complete.
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