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Scan Tool Does Not Communicate With Class 2 Serial Data Line

NOTE: To identify components on class 2 serial data line, see DATA LINK CONNECTORS article in WIRING DIAGRAMS.
  1. Connect scan tool to DLC. Turn ignition on. If scan tool works, go to next step. If scan tool does not work, go to SCAN TOOL DOES NOT POWER UP .
  2. Attempt to communicate with vehicle modules using scan tool. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  5.
  3. Check DTCs for each module. Record each DTC, status (history or current) and which module set the DTC. If any communication DTCs (DTCs with "U" prefix) are present, go to next step. If no communication DTCs are present, go to STANDARD BODY MODULE (SBM) DIAGNOSTIC SYSTEM CHECK .
  4. Go to appropriate test under DIAGNOSTIC TESTS. See DTC IDENTIFICATION  table under SELF-DIAGNOSTIC SYSTEM.
  5. Turn ignition switch to OFF position. Disconnect scan tool from DLC. Ensure connections of DLC are clean and tight. Check for any terminals that are not seated properly. If connections are okay, go to next step. If faulty connections are found, repair as necessary. Recheck system.
  6. Check for open or poor connection on Black/White wire between DLC terminal No. 5 and G202, located under driver's side kick panel. If no problem is found, go to next step. If problem is found, repair as necessary. Recheck system.
  7. Disconnect Gray 16-pin connector C200. C200 is located in body-to-instrument panel harness under left side of instrument panel, to left of steering column. Check continuity of Purple wire between DLC terminal No. 2 and connector C200 terminal "A". If continuity exists, go to next step. If continuity does not exist, repair as necessary. Recheck system.
  8. Disconnect 68-pin rear fuse block connector C1, located under rear seat. Disconnect Gray 68-pin Instrument Panel (IP) fuse block connector C1, located under passenger's side of instrument panel. Connect scan tool. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  14.
  9. Turn ignition off. Reconnect rear fuse block connector C1. Disconnect Black 68-pin rear fuse block connector C2. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  24.
  10. Turn ignition off. Reconnect IP fuse block connector C1. Disconnect Brown 68-pin IP fuse block connector C4, located under passenger's side of instrument panel. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  25.
  11. Turn ignition off. Reconnect rear fuse block connector C2. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  19.
  12. Turn ignition off. Reconnect IP fuse block connector C4. Disconnect Gray 10-pin connector C101, located between body harness and engine harness at right rear of engine compartment. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  23.
  13. Turn ignition off. Reconnect connector C101. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to step  27. If scan tool does not communicate, go to step  19.
  14. Turn ignition off. Disconnect Gray 16-pin connector C200. C200 is located between body harness and instrument panel harness under left side of instrument panel, to left of steering column. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  19.
  15. Turn ignition off. Disconnect Driver's Door Module (DDM) connectors. Reconnect connector C200. Using scan tool, attempt to communicate with vehicle modules still connected. If scan tool communicates with any module, go to next step. If scan tool does not communicate, go to step  18.
  16. Turn ignition off. Check for short to ground or short to power (ignition on) on Purple wire between DDM harness connector C1 terminal No. 3 and rear fuse block connector C1 terminal D11. If no short is found, go to next step. If short is found, repair as necessary. After repairs, recheck system.
  17. Replace DDM. See ANTI-THEFT SYSTEMS - PARK AVENUE article.
  18. Turn ignition off. Check for short to ground or short to power (ignition on) on Purple wire between DDM harness connector C1 terminal No. 13 and connector C200 terminal "A". If no short is found, go to next step. If short is found, repair as necessary. Recheck system.
  19. Turn ignition off. Disconnect SBM connectors. Turn ignition on. Using scan tool, attempt to communicate with vehicle modules still connected. Turn ignition off. Repeat procedure, disconnecting the following modules one at a time; MSM, HCM, SDM, IPC, RFA, VTD and DDM. If communication is possible at any time before disconnecting the last module, stop disconnecting modules and go to next step. If there is no communication after disconnecting all modules, go to step  23.
  20. Turn ignition off. Check for short to ground or short to power (ignition on) on serial data circuit (Purple wire) after disconnected module. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If no short is found, go to next step. If short is found, repair as necessary. After repairs, go to step  26.
  21. Check harness connector and module terminals for poor connection and damage. If no problem is found, go to next step. If any problem is found, repair as necessary. After repairs, go to step  26.
  22. Replace last module disconnected. After repairs, go to step  26.
  23. Repair serial data circuit between DDM connector C1 terminal No. 13 and DLC terminal No. 2. After repairs, go to step  26.
  24. Turn ignition off. Replace rear fuse block. After repairs, go to step  26.
  25. Turn ignition off. Replace IP fuse block. After repairs, go to step  26.
  26. Reconnect all components and connectors. Connect scan tool. Turn ignition on. If scan tool will not communicate, disconnect and reconnect scan tool (power up reset). After 10 seconds, check DTCs for each module. Record each DTC, status (history or current) and which module set the DTC. If no current "U" prefix codes exist, go to next step. If any "U" prefix codes are current, go to step  28.
  27. If any other (non-"U" prefix) DTCs exist, go to next step. If no other DTCs exist, go to step  29.
  28. If DTC P1602-P1615 or P1626 are set and vehicle will start and run, ignore DTCs and go to next step. Diagnose and repair remaining DTCs. See appropriate article. After repair, go to next step.
  29. Turn ignition on. Using scan tool, clear DTCs.
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