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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 266 (BODY CONTROL MODULES)DIAGNOSTIC TESTSDTC U1000 & U1255: CLASS 2 COMMUNICATION MALFUNCTIONTEST PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Test Procedure

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Procedure
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. 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 driver side of instrument panel, near steering column. Using scan tool, retrieve DTCs. If DTCs U1001-U1254 are not retrieved as history, go to next step. If DTCs U1001-U1254 are retrieved as history, repair those DTCs first. Perform DTC U1001-U1254: LOSS OF XXX COMMUNICATION .
  2. Turn ignition switch to RUN position. Using scan tool, attempt to communicate with each module on Class 2 serial data circuit. See DESCRIPTION . If any modules on Class 2 serial data circuit do not communicate, go to next step. If all modules on Class 2 serial data circuit communicate, go to step  12.
  3. Inspect battery voltage, ignition voltage input and output circuits for an open or short to ground for modules not communicating. See CONNECTOR IDENTIFICATION . See WIRING DIAGRAMS . If problem does not exist, go to next step. If problem exists, repair battery voltage, ignition voltage input and/or output circuits as necessary. After repair, go to step  8.
  4. Turn ignition switch to OFF position. Inspect ground circuits for an open for modules not communicating. See CONNECTOR IDENTIFICATION . See WIRING DIAGRAMS . If problem does not exist, go to next step. If problem exists, repair ground circuits as necessary. After repair, go to step  8.
  5. Inspect Purple Class 2 data wire of module not communicating for an open. See CONNECTOR IDENTIFICATION . See WIRING DIAGRAMS . If problem does not exist, go to next step. If problem exists, repair Purple Class 2 data wire as necessary. After repair, go to step  8.
  6. Inspect suspect module harness connector for poor connections and terminal tension. If problem does not exist, go to next step. If problem exists, repair suspect module harness connector as necessary. After repair, go to step  8.
  7. Replace module which was not communicating. See REMOVAL & INSTALLATION . Program module, if necessary. See PROGRAMMING . After repair, go to step  10.
  8. Connect scan tool to DLC. Turn ignition switch to RUN position. Using scan tool, select DISPLAY DTCs function for module which was not communicating. If scan tool does not display any DTCs which do not begin with "U", go to next step. If scan tool displays any DTCs which do not begin with "U", perform appropriate diagnostic system check to diagnose DTCs. See BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  9. Using scan tool, clear DTCs, then go to next step.
  10. Using scan tool, select DISPLAY DTCs function for module(s) which stored U1000 or U1255 as current. If scan tool does not display DTCs which do not begin with "U", go to next step. If scan tool displays DTCs which do not begin with "U", perform appropriate diagnostic system check to diagnose DTCs. See BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  11. Using scan tool, clear DTCs. System is okay at this time.
  12. If there are no other DTCs for modules which stored U1000 or U1255 as current, go to next step. If other DTCs for module which stored U1000 or U1255 as current, perform appropriate diagnostic system check to diagnose DTCs. See BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  13. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 5 seconds. Turn ignition switch to RUN position. Using scan tool, select DISPLAY DTCs function. If scan tool displays DTC U1000 or U1255 as current, go to next step. If scan tool does not display DTC U1000 or U1255 as current, see DIAGNOSTIC AIDS .
  14. Replace module which stored U1000 or U1255 as current. See REMOVAL & INSTALLATION . Program module, if necessary. See PROGRAMMING . System is okay at this time.
RENDER: 1.0x

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