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

  1. Ensure battery condition, cold cranking amperage and reserve capacity meet specifications. Replace as necessary. Install 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 TEST B: SCAN TOOL DOES NOT POWER UP  under SYSTEM TESTS.
  2. Turn ignition on, with engine off. Try to establish scan tool communication with each module on class 2 serial data circuit. (On Tech II scan tools, CLASS 2 MESSAGE MONITOR feature). If communication with any module is established, go to next step. If communication with any module is not established, go to step  6
  3. Select DISPLAY DTC function for each module on class 2 serial data circuit. Record all displayed DTCs, status of displayed DTCs and module that set DTC. If any DTCs in range of U1000 to U1305 are displayed, go to next step. If no DTCs in range of U1000 to U1305 are displayed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
  4. If DTCs U1300, U1301 or U1305 are displayed, go to step  14 . If DTCs U1300, U1301 or U1305 are not displayed, go to next step.
  5. If DTC U1000 or U1255 is the only DTC displayed, go to DTC U1000 & DTC U1255: CLASS 2 COMMUNICATION FAULT  under DIAGNOSTIC TESTS. If DTC U1000 or U1255 is not the only DTC displayed, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
  6. Turn ignition off. Disconnect scan tool from DLC. Inspect DLC terminal No. 2 (Brown/White wire) and terminal No. 5 (Black wire) for poor connections. See Figure . If connections are okay, perform diagnostic system check for malfunctioning system or device. If DLC malfunction was not located and repaired, go to next step.
  7. Using a DVOM, test DLC ground circuit terminal No. 5 (Black wire) for an open. See WIRING DIAGRAMS  . If circuit is okay, perform diagnostic system check for malfunctioning system or device. If malfunction was not located and repaired, go to next step.
  8. Turn ignition off. Disconnect all modules on class 2 serial data circuit which includes Body Control Module (BCM), cellular telephone, radio, Radio Integration Module (RIM), OnStar(R) Vehicle Integration Unit (VIU) and remote control door lock receiver. See COMPONENT LOCATIONS  . Check class 2 serial data circuit (Brown/White wire) for short to ground (ignition off) and for short to voltage (ignition on) between DLC connector terminal No. 2 and each module. If malfunction was located and repaired, go to step  14 . If malfunction was not located and repaired, go to next step.
  9. Reconnect BCM and all disconnected in-line harness connectors. Install scan tool to DLC. Turn ignition on and attempt communication with BCM. If scan tool communicates with BCM, go to next step. If scan tool does not communicate with BCM, go to step  11 .
  10. Continue reconnecting modules on class 2 serial data circuit one at a time and attempting to communicate after each connection until communication cannot be established or all modules are reconnected. When attempted class 2 serial data circuit communications cannot be established, go to step  12 . If communication can be established and all modules are reconnected, go to DIAGNOSTIC AIDS  .
  11. Inspect for poor connections of class 2 serial data circuit (Brown/White wire) at BCM connector C1 terminal B9. See Figure . If malfunction was located and repaired, go to step  14 . If malfunction was not located and repaired, go to step  13 .
  12. Inspect for poor connections of class 2 serial data circuit (Brown/White wire) at most recently reconnected module. If malfunction was not located and repaired, replace most recently reconnected module. See REMOVAL & INSTALLATION  . After replacement, go to step  14 . If malfunction was located and repaired, go to step  14 .
  13. Replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION. After replacement, perform set up procedure. See PROGRAMMING  . After replacement, go to next step.
  14. Turn ignition off. Reconnect all disconnected modules and any remaining disconnected connectors. Install scan tool to DLC. Turn ignition on, with engine off. Wait 10 seconds in case scan tool must reset due to a short on class 2 serial data circuit. Turn off or disconnect scan tool before proceeding. Reinstall or turn scan tool on and select DISPLAY DTCs function for each module on class 2 serial data circuit. Record all displayed DTCs, status of displayed DTCs and module that set DTC. If any DTCs that begin with "U" are displayed as CURRENT, go to step  16 . If no DTCs that begin with "U" are displayed as CURRENT, go to next step.
  15. If any DTCs were recorded that did not begin with "U", go to next step. If DTCs were recorded that did begin with "U", go to step  18 .
  16. Diagnose and repair recorded DTCs. Perform appropriate diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . For DTCs not listed, go to appropriate article for malfunctioning system or module. After repair, go to next step.
  17. If all DTCs have been diagnosed, go to next step. If all DTCs have not been diagnosed, repeat step  16 .
  18. Use scan tool to clear DTCs. See CLEARING DTCS  under SELF-DIAGNOSTIC SYSTEM. Check is complete.
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