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Scan Tool Does Not Communicate With UART Data Line

WARNING: This page is about a different car, the 1999 GMC Sierra and 1999 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  2. If the scan tool does not power up, go to next step. If scan tool powers up, go to step  10 .
  3. Disconnect the scan tool from data link connector (DLC). Inspect for a proper connection of the scan tool to the DLC at terminals No. 2 and 16. If the connection is good, go to next step. If the connection is faulty, go to step  6 .
  4. Measure the voltage from terminal No. 16 of the DLC to ground. If voltage is 12-14.6 volts, go to next step. If voltage is not 12-14.6 volts, go to step  8 .
  5. Measure the resistance from terminal No. 4 of the DLC to ground. If the resistance is 0-5 ohms, go to step  7 . If the resistance is not 0-5 ohms, go to step  9 .
  6. Repair the connection. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  7. The scan tool may be malfunctioning. Refer to the scan tool instruction manual. Go to step  2 .
  8. Repair the open in CKT 640 (Orange wire). Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  9. Repair the open in CKT 1850 (Black wire). Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  10. Inspect for a proper connection of the scan tool to the DLC at terminal No. 9. If connection is okay, go to next step. If connection is faulty, go to step  6 .
  11. Disconnect the inflatable restraint sensing and diagnostic module. See REMOVAL & INSTALLATION in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS. Inspect for a proper connection to the inflatable restraint sensing and diagnostic module at terminal No. 5. If connection is okay, go to next step. If connection is faulty, go to step  19 .
  12. Measure the resistance from terminal No. 9 of the DLC to terminal No. 5 of the inflatable restraint sensing and diagnostic module. If the resistance is 0-5 ohms, go to next step. If the resistance is not 0-5 ohms, go to step  18 .
  13. Measure the resistance on the DLC from terminal No. 9 to terminal No. 4. If there is no continuity, go to next step. If there is continuity, go to step  17 .
  14. Turn the ignition switch to the RUN position. Measure the voltage on the DLC from terminal No. 9 to terminal No. 4. If the voltage is 0-1 volts, go to next step. If the voltage is not 0-1 volts, go to step  16 .
  15. Turn the ignition switch to the OFF position. Replace the inflatable restraint sensing and diagnostic module. See REMOVAL & INSTALLATION in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  16. Turn the ignition switch to the OFF position. Repair the short to voltage in CKT 800. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  17. Repair the short to ground in CKT 800. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  18. Repair the open in CKT 800. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
  19. Repair the connection. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING in AIR BAG RESTRAINT SYSTEM - TRUCKS article in RESTRAINTS.
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