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

WARNING: This page is about a different car, the 2001 GMC Safari and 2001 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Install scan tool. If scan tool works, go to next step. If scan tool does not work, go to TEST E: SCAN TOOL DOES NOT POWER UP  under SYSTEM TESTS.
  2. Turn ignition switch to RUN position. 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  7 .
  3. Check DTCs for each module. Record each DTC, status (history or current) and which module set DTC. If any communication DTCs between U1000 to U1255 exist, go to next step. If no communication DTCs exist, see DIAGNOSTIC AIDS  .
  4. If DTCs U1300, U1301 or U1305 are retrieved from any module, go to next step. If DTCs U1300, U1301 or U1305 are not retrieved from any module, go to step  6 .
  5. Test class 2 serial data circuit, terminal No. 2 (Purple wire) at Data Link Connector (DLC) for an intermittent short to ground or an intermittent short to voltage. If problem is found, repair as necessary. After repair, go to step  29 . If no problem was found, go to next step.
  6. If only U1000 or U1255 exist, go to DTC U1000 & U1255: CLASS 2 COMMUNICATION MALFUNCTION  . If any other "U" codes exist, go to DTC U1001-U1254: LOSS OF XXX COMMUNICATIONS  .
  7. Turn ignition switch to OFF position. Disconnect scan tool from DLC. Check DLC terminals No. 2 (Purple wire) and No. 5 (Black wire) for proper contact. If no problem is found, go to next step. If any looseness or damage exists, repair as necessary. After repair, go to DIAGNOSTIC SYSTEM CHECK INDEX  table under SELF-DIAGNOSTIC SYSTEM.
  8. Check for open circuit between DLC terminal No. 5 (Black 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 repair, go to DIAGNOSTIC SYSTEM CHECK INDEX  table under SELF-DIAGNOSTIC SYSTEM.
  9. With Natural 12-pin splice pack SP261 connector assembled, located below data link connector (DLC). Check for continuity from terminal "A" (Purple wire) to every other terminal in connector. See Figure . Remove comb from between terminals. 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 repair, go to DIAGNOSTIC SYSTEM CHECK INDEX  table under SELF-DIAGNOSTIC SYSTEM.
  10. Check for open or short on Purple wire between DLC terminal No. 2 and splice pack SP261 harness connector terminal "A". If no problem is found, go to next step. If problem is found, repair open or short condition. After repair, go to DIAGNOSTIC SYSTEM CHECK INDEX  table under SELF-DIAGNOSTIC SYSTEM.
  11. Connect a jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "M" (Light Green wire). Turn ignition switch to RUN position. Attempt to communicate with BCM. If BCM will not communicate, go to next step. If BCM communicates, go to step  13 .
  12. Turn ignition switch to OFF position. Disconnect BCM harness connectors C1 (Brown). Check for short to ground, or short to power (ignition switch in RUN position) on Light Green wire between BCM connector C1 (Brown) terminal A12 and splice pack SP261 terminal "M". See Figure . If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 .
  13. Leave jumper wire from step  11 connected. Connect another jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "B" (Dark Green wire). Turn ignition switch to RUN position. Attempt to communicate with PCM. If PCM will not communicate, go to next step. If PCM communicates, go to step  15 .
  14. Turn ignition switch to OFF position. Disconnect PCM connector C1 (Blue). Check for short to ground, or short to power (ignition switch in RUN position) on Dark Green wire between PCM connector C4 terminal No. 58 and splice pack SP261 terminal "B". If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 .
  15. Leave jumper wire from step  11 connected. Remove jumper wire from splice pack SP261 connector terminal "B"(to PCM). Connect jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "C" (Dark Green/White wire). Turn ignition switch to RUN position. Attempt to communicate with Automatic Transfer Case Shift Control Module (ATC/TCSCM). If ATC/TCSCM will not communicate, go to next step. If transfer case shift control module communicates, go to step  17 .
  16. Turn ignition switch to OFF position. Disconnect harness connector C1 from ATC/TCSCM . Check for short to ground, or short to power (ignition switch in RUN position) on Dark Green/White wire between transfer case shift control module connector C1 terminal No. E9 and splice pack SP261 terminal "C". See DATA LINK CONNECTORS articles in WIRING DIAGRAMS. If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 .
  17. Leave jumper wire from step  11 connected. Remove jumper wire from ATC/TCSCM class 2 circuit. Remove jumper wire from splice pack SP261 connector terminal "C". Connect jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "E" (Light Blue wire). Turn ignition switch to RUN position. Attempt to communicate with Electronic Brake Control Module (EBCM). If EBCM will not communicate, go to next step. If EBCM communicates, go to step  19 .
  18. Turn ignition switch to OFF position. Disconnect EBCM connectors. Check for short to ground, or short to power (ignition switch in RUN position) on Light Blue wire between EBCM connector C1 terminal B6 and splice pack SP261 terminal "E". If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 .
  19. Leave jumper wire from step  11 connected. Remove jumper wire from EBCM class 2 circuit. Remove jumper wire from splice pack SP261 connector terminal "E". Connect jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "F" (Dark Blue wire). Turn ignition switch to RUN position. Attempt to communicate with SDM. If SDM will not communicate, go to next step. If SDM communicates, go to step  21 .
  20. Turn ignition switch to OFF position. Disconnect SDM connector. Check for short to ground, or short to power (ignition switch in RUN position) on Dark Blue wire between SDM connector terminal No. 4 and splice pack SP261 terminal "F". If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 .
  21. Leave jumper wire from step  11 connected. Remove jumper wire from SDM class 2 circuit. Remove jumper wire from splice pack SP261 connector terminal "F". Connect jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "G" (Gray wire). Turn ignition switch to RUN position. Attempt to communicate with Instrument Panel Cluster (IPC). If instrument panel cluster will not communicate, go to next step. If instrument cluster communicates, go to step  23 .
  22. Turn ignition switch to OFF position. Disconnect instrument cluster connector. Check for short to ground, or short to power (ignition switch in RUN position) on Gray wire between instrument cluster connector terminal B5 and splice pack SP261 terminal "G". If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 .
  23. Leave jumper wire from step  11 connected. Remove jumper wire from splice pack SP261 connector terminal "G". Connect jumper wire between splice pack SP261 connector terminals "A" (Purple wire) and "K" (Yellow wire). Turn ignition switch to RUN position. Attempt to communicate with Driver Information Center (DIC). If DIC will not communicate, go to next step. If DIC communicates, go to step  25 .
  24. Turn ignition switch to OFF position. Disconnect DIC connector. Check for short to ground, or short to power (ignition switch in RUN position) on Yellow wire between DIC connector C303 and splice pack SP261 terminal "K". If no problem is found, go to next step. If problem is found, repair as necessary. After repair, go to step  29 .
  25. Turn ignition switch to OFF position. Disconnect DIC connector. Connect jumper wire to each end of redundant PCM/BCM class 2 circuit, PCM harness connector C1 (Blue) terminal No. 59 (Yellow wire) and BCM harness connectors C2 (Light Blue wire) terminal A1 (Yellow wire). Attempt to view all data on overhead display. If no problem is found, go to next step. If problem is found, go to step  27 .
  26. Turn ignition switch to OFF position. Disconnect BCM harness connectors C1 (Brown) terminal A12 (Light Green wire). Check for short to ground, or short to power (ignition switch in RUN position) on redundant PCM/BCM class 2 circuit. If no problem is found, go to step  27 . If problem is found, repair as necessary. After repair, go to step  29 . Replace module that is not communicating. See appropriate article for replacement and programming information. After repair, go to next step.
  27. Check for poor or loose connection at connectors terminals of modules that are not communicating. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, go to step  29 .
  28. Replace module that is not communicating see REMOVAL & INSTALLATION  . After repair, go to next step.
  29. Reinstall components, Connect all of modules. Connect any other connectors. Connect a scan tool. Turn ignition switch to ON position, engine off. Wait for 10 Seconds. Scan tool may require a power up reset before communication will occur due to a short ON class 2 circuit. Turn off or disconnect scan tool prior to performing this test. Select display DTCs function for each module. If using a Tech 2, use class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all displayed DTCs and DTC status. If you record any DTCs which begin with a "U" and with a current status. Go to step  31 . If you did not record any DTCs which begin with a "U" and with a current status. Go to next step.
  30. If you record any DTCs which did not begin with a "U" , go to next step. If you record any DTCs which began with a "U" go to step  32 .
  31. Diagnose and repair all DTCs as necessary, except history "U" codes (set during testing). See appropriate article for test procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . After all repairs are complete, go to next step.
  32. Using scan tool, clear all DTCs. Recheck for DTCs. If all DTCs are cleared, systems are operating properly.
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