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Scan Tool Does Not Communicate With Class 2 Device

  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. See CLASS 2 SERIAL DATA LINE  under OPERATION. If scan tool communicates with any module, go to next step. If scan tool does not communicate with any module, go to step  6 .
  3. Display DTC's for each module. If any DTCs between U1000 and U1255 are set, go to next step. If no DTCs between U1000 and U1255 are set, go to step  5 .
  4. If only DTC U1000 or U1255 are set, go to DTC U1000 & U1255: CLASS 2 COMMUNICATION MALFUNCTION  under DIAGNOSTIC TESTS. If DTCs between U1000 are U1255 are set, go to DTC U1001-U1254: LOSS OF XXX COMMUNICATIONS  under DIAGNOSTIC TESTS.
  5. Diagnose malfunction using DTC U1001-U1254: LOSS OF XXX COMMUNICATIONS  under DIAGNOSTIC TESTS. After repairs, go to BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK  . If sent here from another article, return to that article and perform diagnostic system check.
  6. Turn ignition off. Disconnect scan tool from DLC. Check for poor connections at DLC terminals No. 2 (Purple wire) and No. 5 (Black wire). If connections are okay, go to next step. If faulty connections are found and repaired, go to BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK  . If sent here from another article, return to that article and perform diagnostic system check.
  7. Check for open in Black wire between DLC terminal No. 5 and ground G203. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. G203 is located behind left front kick panel. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK  . If sent here from another article, return to that article and perform diagnostic system check.
  8. Check for open in Purple wire between DLC terminal No. 2 and splice S203. S203 is located near harness breakout for Sensing And Diagnostic Module (SDM) located under driver's seat. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to BODY CONTROL MODULE DIAGNOSTIC SYSTEM CHECK  . If sent here from another article, return to that article and perform diagnostic system check.
  9. Disconnect Powertrain Control Module (PCM) connectors. PCM is located in left front corner of engine compartment, under air filter housing. Connect scan tool to DLC. Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  11 .
  10. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION - CARS article in ENGINE PERFORMANCE. After repairs, go to step  52 .
  11. Disconnect Electronic Brake Control Module (EBCM) connectors. See Fig 1 . Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  14 .
  12. Check for short to ground or short to voltage in Purple wire between EBCM connector C2 terminal No. 10 and PCM connector C1 terminal No. 58. See Fig 2 and Fig 3 . Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .
    Fig 1: Locating Electronic Brake Control Module
    G00020237Courtesy of GENERAL MOTORS CORP.
    Fig 2: Identifying Electronic Brake Control Module Connector Terminals
    G00020241Courtesy of GENERAL MOTORS CORP.
    Fig 3: Identifying PCM Connector C1 & C2 Terminals
    G00012127Courtesy of GENERAL MOTORS CORP.
  13. Replace EBTCM. See ELECTRONIC BRAKE CONTROL MODULE  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  14. Turn ignition off. Disconnect radio connector. See RADIO  under REMOVAL & INSTALLATION. Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  16 .
  15. Replace radio. After replacement, go to step  52 .
  16. Turn ignition off. Disconnect Instrument Panel Cluster (IPC) connector. See ANALOG INSTRUMENT PANELS - SEVILLE article. Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  18 .
  17. Replace IPC. See ANALOG INSTRUMENT PANELS - ELDORADO article. After replacement, go to step  52 .
  18. Turn ignition off. Disconnect A/C-heater control panel. Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  21 .
  19. Check for short to ground or short to voltage in Purple wire between A/C-heater control panel connector terminal A8 and IPC connector C3 terminal D1. See Figure . Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired go to step  52 .
  20. Replace A/C-heater control panel. See A/C-HEATER CONTROL PANEL  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  21. If vehicle is equipped with A45 (Memory Personalization Package), go to next step. If vehicle is not equipped with A45, go to step  25 .
  22. Turn ignition off. Disconnect Memory Mirror Module (MMM) connector. Module is located under left side of instrument panel above brake pedal. See Fig 4 . Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  25 .
  23. Check for short to ground or short to voltage in Purple wire between MMM connector terminal E16 and A/C-heater control panel connector terminal A8. See Fig 5 and Fig 6 . Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .
  24. Replace MMM. See MEMORY MIRROR MODULE  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  25. Turn ignition off. Disconnect A/C-heater programmer. Programmer is located behind the glove box. Turn ignition on. Attempt to communicate with PZM. See Fig 7 . If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  28 .
    Fig 4: Locating Memory Mirror Module
    G00020265Courtesy of GENERAL MOTORS CORP.
    Fig 5: Identifying Memory Mirror Module & Radio Connector Terminals
    G00020245Courtesy of GENERAL MOTORS CORP.
    Fig 6: Identifying A/C-Heater Control Panel Connector Terminals
    G00016868Courtesy of GENERAL MOTORS CORP.
    Fig 7: Locating A/C-Heater Programmer
    G98G03394Courtesy of GENERAL MOTORS CORP.
  26. Check for short to ground or short to battery voltage in Purple wire between A/C-heater programmer connector C2 terminal D2 and one of the following components:
    • MMM connector terminal F16 (with A45).
    • A/C-heater control panel connector terminal B8 (without A45).

    Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .

  27. Replace A/C-heater programmer. See A/C-HEATER PROGRAMMER  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  28. If vehicle is equipped with factory cellular telephone, go to next step. If vehicle is equipped with aftermarket cellular telephone or has no telephone at all, go to step  31 .
  29. Turn ignition off. Disconnect cellular telephone module connector. Module is located in the right side of rear compartment, near power antenna motor. Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  31 .
  30. Replace cellular telephone module. See CELLULAR TELEPHONE MODULE  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  31. If vehicle is equipped with A45 (Memory Personalization Package), go to next step. If vehicle is not equipped with A45, go to step  35 .
  32. Turn ignition off. Disconnect Memory Seat Module (MSM) connector. Module is located under driver's seat. See Fig 8 . Turn ignition on. Attempt to communicate with PZM. Turn ignition on. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  35 .
  33. Check for short to ground or short to voltage in Purple wire between MSM connector C1 terminal No. 26 and radio connector terminal E6. See Fig 5 and Fig 9 . Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .
    Fig 8: Locating Power Seat Components
    G95E35158Courtesy of GENERAL MOTORS CORP.
    Fig 9: Identifying MSM Connector C1 Terminals
    G98F01728Courtesy of GENERAL MOTORS CORP.
  34. Replace MSM. See MEMORY SEAT MODULE  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  35. Turn ignition off. Disconnect Sensing and Diagnostic Module (SDM) connector. Module is located under driver's seat. Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  38 .
  36. Check for short to ground or short to voltage in Purple wire between SDM connector terminal No. 17 and one or more of the following components:
    • MSM connector C1 terminal No. 25 (with A45).
    • Radio connector terminal E6 (without A45).

    Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .

  37. Replace SDM. See AIR BAG RESTRAINT SYSTEMS - DEVILLE, ELDORADO & SEVILLE article. After repairs, go to step  52 .
  38. If vehicle is equipped with F45 (Real Time Dampening), go to next step. If vehicle is not equipped with F45, go to step  41 .
  39. Turn ignition off. Disconnect Continuous Variable Road Sensing Suspension (CVRSS) module connector. Module is located behind rear seat back on right side. See Figure . Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  41 .
  40. Replace CVRSS module. See CONTINUOUS VARIABLE ROAD SENSING SUSPENSION MODULE  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  41. If vehicle is equipped with UQ4 (4-speaker Bose system), go to next step. If vehicle is not equipped with UQ4, go to step  46 .
  42. Turn ignition off. Disconnect Radio Interface Module (RIM). See Figure . Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  46 .
  43. If vehicle is equipped with F45 (Real Time Dampening), go to next step. If vehicle is not equipped with F45, go to step  46 .
  44. Check for short to ground or short to voltage in Purple wire between CVRSS module connector C1 terminal D5 and RIM connector C1 terminal B2. See Figure . Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .
  45. Replace RIM. See RADIO INTERFACE MODULE  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  46. Turn ignition off. Disconnect the Remote Function Actuator (RFA). RFA is located behind center of rear seat back. See Figure . Turn ignition on. Attempt to communicate with PZM. If scan tool communicates with PZM, go to next step. If scan tool does not communicate with PZM, go to step  50 .
  47. If vehicle is equipped with F45 or UQ4, go to next step. If vehicle is not equipped with F45 or UQ4, go to step  49 .
  48. Check for short to ground or short to voltage in Purple wire between RFA module connector terminal No. 2 and one or more of the following components:
    • CVRSS module connector C1 terminal D5 (with F45 and without UQ4).
    • RIM connector C1 terminal B3 (without F45 and with UQ4).

    Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .

  49. Replace RFA module. See REMOTE FUNCTION ACTUATOR  under REMOVAL & INSTALLATION. After replacement, go to step  52 .
  50. Check for short to ground or short to voltage in Purple wire between the following components:
    • EBCM connector C2 terminal No. 26 and PZM connector C1 terminal A1.
    • RFA connector terminal No. 3 and PZM connector C1 terminal A2.

    Turn ignition on when testing for short to voltage. If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  52 .

  51. Replace PZM. See PLATFORM ZONE MODULE  under REMOVAL & INSTALLATION. After repairs, go to next step.
  52. Turn ignition off. Reconnect all disconnected modules and connectors. Connect scan tool to DLC. Turn ignition on. Wait 10 seconds and display DTCs for each module along the class 2 serial data line. See CLASS 2 SERIAL DATA LINE  under OPERATION. If any DTCs that begin with "U" are not set as current, go to next step. If any DTCs that begin with "U" are set as current, go to step  54 .
  53. If any DTCs that do not begin with "U" are set, go to next step. If not DTCs are set, go to step  56 .
  54. Diagnose DTCs for module they are set. If DTC P1602 is set in PCM and vehicle will start and run, repair is complete. After repairs, go to next step.
  55. If all DTCs have been diagnosed and repaired, go to next step. If all DTCs have not been diagnosed and repaired, go to step  54 .
  56. Use scan tool to clear any history DTCs. Recheck system operation.
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