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Test B: Scan Tool Does Not Communicate With Class 2 Device: Testing

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect scan tool to Data Link Connector (DLC). DLC is located below left side of instrument panel. If scan tool powers up, go to next step. If scan tool does not power up, perform TEST A: SCAN TOOL DOES NOT POWER UP .
  2. Turn ignition switch to RUN position. Attempt to communicate with each modules on class 2 serial data circuit. If scan tool communicates with any module, go to next step. If scan tool does not communicate with any module, go to step  5.
  3. Using scan tool, select DISPLAY DTCs function for each module. Record all DTCs, status of DTCs and module which set DTC. If DTCs U1000-U1305 are displayed, go to next step. If DTCs U1000-U1305 are not displayed, see DIAGNOSTIC AIDS .
  4. If DTC U1300, U1302 or U1305 are displayed, go to next step. If DTC's are not displayed, go to step  6.
  5. Inspect class 2 serial data circuit for an intermittent short to ground or voltage. If short is found, repair as necessary and go to step  21. If no short is found, go to next step.
  6. If U1000 is the only DTC displayed, then go to DTC U1000 & U1255: CLASS 2 COMMUNICATION MALFUNCTION  under DIAGNOSTIC TESTS. If U1000 is not the only DTC displayed, then go to DTC U1001-U1254: LOSS OF XXX COMMUNICATIONS  under DIAGNOSTIC TESTS.
  7. Turn ignition OFF. Disconnect scan tool from DLC. Inspect DLC for poor connections at terminal 2 and 5. If condition is found, repair as necessary then perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK , under SELF-DIAGNOSTIC SYSTEM. If no condition is found, go to next step.
  8. Inspect Purple wire for an open or short between DLC connector terminal No. 2 and a good ground circuit. If an open or short is not found, go to next step. If an open or short is found, repair as necessary then perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  table under SELF-DIAGNOSTIC SYSTEM.
  9. Disconnect star connector. Inspect for poor connections at star connector. If poor connection is found, repair as necessary then perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  table under SELF-DIAGNOSTIC SYSTEM. If no poor connection is found, go to next step.
  10. Test class 2 serial data circuit for an open or a short between the DLC connector and the star connector. If open or short is found, repair as necessary then perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  table under SELF-DIAGNOSTIC SYSTEM. If no open or short is found, go to next step.
  11. Connect a 3A fused jumper to the DLC terminal of the star connector. Connect other end of jumper to PCM terminal of star connector. See Figure. Turn ignition to RUN position. Attempt to communicate with the 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 switch to OFF position. Disconnect PCM. Test class 2 serial data circuit between the star connector and the PCM for a short to ground or a short to voltage. Turn ignition to RUN position when testing for a short. If short is found, repair as necessary and go to step  21. If no short is found, go to step  19.
  13. Disconnect jumper wire from PCM terminal of star connector. Connect jumper wire to the SDM terminal of the star connector. See Figure. Turn ignition to RUN position. Attempt to communicate with the SDM. If scan tool communicates with the SDM, go to step  15. If scan tool does not communicate with the SDM, go to next step.
  14. Turn ignition switch to OFF position. Disconnect SDM. Test the class 2 serial data circuit between the star connector and the SDM for a short to ground or a short to voltage. Turn ignition to RUN position when testing for a short to voltage. If short is found, repair as necessary then go to step  21. If no short is found, go to step  19.
  15. Remove jumper wire from SDM terminal of star connector. Connect jumper wire to the EBCM terminal of the star connector. See Figure. Turn ignition to RUN position. Attempt to communicate with the EBCM. If scan tool communicates with the EBCM, go to step  17. If scan tool does not communicate with the EBCM, go to next step.
  16. Turn ignition switch to OFF position. Disconnect EBCM. Test the class 2 serial data circuit between the star connector and the EBCM for a short to ground or voltage. Turn ignition to RUN position when testing for short to voltage. If short is found, repair as necessary then go to step  21. If no short is found, go to step  19.
  17. Disconnect jumper wire from the EBCM terminal of the star connector. Connect jumper wire to IPC terminal of the star connector. Turn ignition to RUN position. Attempt to communicate with the IPC. If scan tool communicates with the IPC, go to step  19. If scan tool does not communicate with the IPC, go to next step.
  18. Turn ignition OFF. Disconnect the IPC. Test the class 2 serial data circuit between the star connector and the IPC for a short to ground or voltage. Turn ignition to RUN position when testing for a short to voltage. If short is found, repair as necessary and go to step  21. If no short is found, go to next step.
  19. Inspect class 2 serial data circuit of the module not working for a poor connection. If poor connection is found, repair as necessary and go to step  21. If poor connection is not found, go to next step.
  20. Replace the module that is not communicating, then go to next step.
  21. Reconnect all disconnected modules. Reconnect any other disconnected connectors. Connect scan tool. Turn ignition to RUN position. Wait for 10 seconds. Select display DTC's function for each module. Record all of the DTC's displayed and the status. If you recorded any DTC's that began with a "U", go to step  23. If you recorded any DTC's that did not begin with a "U", go to next step.
  22. If you recorded any DTC's that did not begin with a "U", go to next step. If you recorded any DTC's that did begin with a "U", go to step  24.
  23. Diagnose the DTC's as directed by the diagnostic procedures for the particular module or malfunction, then go to next step.
  24. Clear all the DTC's using the scan tool.
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