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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 170 (BODY CONTROL MODULES)DIAGNOSTIC TESTSDTC U1001-U1254: LOSS OF XXX COMMUNICATIONSTEST PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Test Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION 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 record DTCs. If DTC U1161, U1162, U1163 or U1170 are not retrieved, go to next step. If DTC U1161, U1162, U1163 or U1170 are retrieved, perform DTC U1161-U1163 OR U1170: DRIVER DOOR MODULE COMMUNICATION MALFUNCTION .
  2. Inspect battery or ignition supply voltage circuit to module identified as not communicating for an open. See CONNECTOR IDENTIFICATION . See WIRING DIAGRAMS . If problem does not exist, go to next step. If problem exists, repair battery or ignition supply voltage circuit(s) as necessary. After repair, go to step  8.
  3. Turn ignition switch to OFF position. Inspect ground circuits of module identified as not communicating for an open. If problem does not exist, go to next step. If problem exists, repair ground circuits as necessary. After repair, go to step  8.
  4. Inspect Purple wire for an open for module not communicating. If problem does not exist, go to next step. If problem exists, repair Purple wire as necessary. After repair, go to step  7.
  5. Inspect harness connector of module identified as not communicating for poor connections at battery supply, ignition supply, ground and serial data line terminals. If problem does not exist, go to next step. If problem exists, repair harness connector as necessary. After repair, go to step  8.
  6. Replace module not communicating. See REMOVAL & INSTALLATION . Program module, if necessary. See PROGRAMMING . After repairs, go to step  8.
  7. Connect scan tool to DLC. Turn ignition switch to RUN position. Using scan tool, select DISPLAY DTCs for module identified as 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 DTC. See BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  8. Using scan tool, select DISPLAY DTCs for module identified as 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 DTC. See BODY CONTROL SYSTEM DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  9. Using scan tool, clear DTCs. Continue diagnosing or clearing DTCs until all modules have been diagnosed.
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