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Scan Tool Does Not Communicate With Class 2 Device: Testing

  1. Connect 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  .
  2. Turn ignition on. Attempt to communicate with each module on class 2 serial data line. If scan tool communicates with one or more modules, go to next step. If scan tool does not communicate with any module, go to step  6 .
  3. Retrieve DTCs for each module. Record DTCs, DTC status and which module set the DTC(s). If any DTCs between DTC U1000 and U1255 are set, go to next step. If no DTCs between DTC U1000 and U1255 are set, go to step  5 .
  4. If only DTC U1000 or U1255 is set, go to DTC U1000 OR U1255: CLASS 2 COMMUNICATION MALFUNCTION  under DIAGNOSTIC TESTS. If other DTC(s) between DTC U1000 and U1255 are set, go to DTC U1001-U1254: LOSS OF COMMUNICATIONS WITH XXX  .
  5. Perform diagnostic procedure for module that is not communicating. See DTC U1001-U1254: LOSS OF COMMUNICATIONS WITH XXX  . Perform appropriate diagnostic system check. See appropriate article for malfunctioning system or device.
  6. Turn ignition off. Disconnect scan tool from DLC. Inspect DLC terminals No. 2 and 5 for poor connections and terminal tension. See Fig 1 . Repair connector as necessary. Perform appropriate diagnostic system check. See appropriate article for malfunctioning system or device. If no problems are found, go to next step.
  7. Check for open circuit between ground and DLC terminal No. 5 (Black/White wire). Ground is located at right "A" pillar. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair ground circuit as necessary. Perform appropriate diagnostic system check. See appropriate article for malfunctioning system or device. If circuit is okay, go to next step.
  8. Check for open in class 2 serial data line (Purple wire) between DLC terminal No. 2 and splice S202 (with heads-up display) or connector C201 terminal A5 (without heads-up display). See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary. Perform appropriate diagnostic system check. See appropriate article for malfunctioning system or device. If circuit is okay, go to next step.
  9. Disconnect Powertrain Control Module (PCM) connector C1. Disconnect Sensing and Diagnostic Module (SDM) harness connector. Connect scan tool to DLC. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  17 .
  10. Turn ignition off. Reconnect PCM connector C1. Disconnect Rear Integration Module (RIM) connector C2. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  12 .
  11. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (Purple wire) between RIM harness connector C2 terminal A12 and SDM harness connector terminal A5. See Fig 2 . See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to step  24 .
  12. Turn ignition off. Disconnect Remote Function Actuator (RFA) harness connector. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  14 .
  13. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (Purple wire) between RFA harness connector terminal No. 3 and harness connector C2 terminal A12. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to step  24 .
  14. Turn ignition off. Disconnect Electronic Brake Control Module (EBCM) connector C1. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  16 .
  15. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (Purple wire) between EBCM harness connector C1 terminal No. 7 and RFA harness connector terminal No. 3. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to step  24 .
  16. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (Purple wire) between PCM harness connector C1 terminal No. 58 and EBCM harness connector C1 terminal No. 21. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to step  24 .
  17. Turn ignition off. Disconnect connector C215. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  20 .
  18. Turn ignition off. Reconnect connector C215. Disconnect Vehicle Theft Deterrent (VTD) module harness connector. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  26 .
  19. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (Purple wire) between PCM harness connector C1 terminal No. 59 and VTD module harness connector terminal "E". See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to step  27 .
  20. Turn ignition off. Disconnect connector C216. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  22 .
  21. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (flex wiring harness) between connector C215 terminal D2 and connector C216 terminal B9. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to step  24 .
  22. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line (Purple wire) between Dash Integration Module (DIM) harness connector C2 terminal A11 and SDM harness connector terminal A4. See Fig 3 . See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary, and go to step  28 . If circuit is okay, go to next step.
  23. Turn ignition off. Check for short to ground and short to voltage in class 2 serial data line at DLC terminal No. 2 (Purple wire). Repair circuit as necessary, and go to step  28 . If circuit is okay, go to next step.
    24. NOTE: DIM must be connected to class 2 serial data line when attempting to communicate.
  24. Reconnect all disconnected modules except those in suspect area of class 2 serial data line. Reconnect any other disconnected harness connectors. Connect one of the disconnect modules in suspect area of class 2 serial data line. Connect scan tool to DLC. Turn ignition on. Attempt to communicate with any module still connected to DLC through class 2 serial data line. If scan tool communicates with any module on class 2 serial data line, go to next step. If scan tool does not communicate with any module on class 2 serial data line, go to step  26 .
  25. Continue connecting disconnected modules and attempting communication until communication cannot be established or all modules are connected. If communication cannot be established after connecting a module, go to step  27 . If communication can be established after all modules are connected, go to step  28 .
  26. Repair class 2 serial data line between VTD module and connector C215. Go to step  28 .
  27. Replace most recently connected module. See appropriate procedure under REMOVAL & INSTALLATION  . Go to next step.
    28. NOTE: Scan tool may require a power up reset before communication if class 2 serial data line was shorted. Turn off or disconnect scan tool before displaying DTCs.
  28. Reconnect all harness connectors. Connect scan tool to DLC. Turn ignition on. Wait 10 seconds. Display DTCs for each module. Record DTCs and DTC status. If any current DTCs beginning with a "U" are displayed, go to step  30 . If no current DTCs beginning with a "U" are displayed, go to next step.
  29. If any DTCs not beginning with a "U" are displayed, go to next step. If no DTCs not beginning with a "U" are displayed, go to step  32 .
  30. Perform appropriate diagnostic procedure. See BODY CONTROL SYSTEM DIAGNOSTIC TROUBLE CODE INDEX  table. For DTCs not listed, go to appropriate article for malfunctioning module or system. PCM may have DTC P1602-P1615 or P1626 set. If only DTC P1602-P1615 or P1626 is set, history DTC(s) beginning with a "U" are set and vehicle will start and run, system is okay. Go to next step.
  31. If all DTCs have been diagnosed, go to next step. If all DTCs have not been diagnosed, go to step  30 .
  32. Using scan tool, clear DTCs. Test is complete.
Fig 1: Identifying Data Link Connector Terminals
G00016046Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying RIM Connectors & Terminals
G00016049Courtesy of GENERAL MOTORS CORP.
Fig 3: Identifying DIM Connectors & Terminals
G00009564Courtesy of GENERAL MOTORS CORP.
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