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Scan Tool Does Not Communicate With UART Data Line

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, check DLC circuit. See WIRING DIAGRAMS .
  2. Turn ignition on, with engine off. Using scan tool, attempt to communicate with each module on the UART data line circuit. If any of the module is communicating with scan tool, go to step 6. If modules are not communicating with scan tool, go to next step.
  3. Check for open in PCM battery positive and ignition circuits. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If circuits are okay, go to next step.
  4. Turn ignition off. Check PCM ground circuits for open. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If ground circuits are okay, go to next step.
  5. Check for open in UART serial data circuit between DLC and PCM. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If circuit is okay, go to next step.
  6. Check for open or short to ground in battery voltage and ignition voltage circuit(s) to module that does not communicate with scan tool. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If circuit is okay, go to next step.
  7. Check for open in ground circuit(s) to module that does not communicate with scan tool. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If circuit is okay, go to next step.
  8. Turn ignition off. Disconnect scan tool from DLC. Disconnect all modules on UART data line circuit. Check for short to ground or short to voltage in UART data line circuit. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If circuit is okay, go to next step.
  9. Check for open in UART serial data circuit between DLC, PCM, EBCM and SDM. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If circuit is okay, go to next step.
  10. Check for poor connections at DLC terminals No. 5 and 9. See WIRING DIAGRAMS . Repair as necessary. After repairs, perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. If connector terminals are okay, go to next step.
  11. Replace faulty module(s). After replacing faulty module(s), perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING.
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