LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> GMC >> 2000 >> Envoy >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock Brake System - 4WAL >> Symptom Diagnosis >> Test C: Scan Tool Does Not Communicate With Class 2 Device
July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

Test C: Scan Tool Does Not Communicate With Class 2 Device

  1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, diagnose data link connector circuit. See DATA LINK CONNECTORS article in WIRING DIAGRAMS.
  2. Turn ignition on, with engine off. Using scan tool, attempt to communicate with each module on class 2 circuit. If scan tool communicates with any module on the class 2 serial data circuit, go to next step. If scan tool does not communicate with any module on the class 2 serial data circuit, go to step  5.
  3. Using scan tool, select display DTCs function for each module. Record all of displayed DTCs, DTC status and module which set the DTC. If recorded DTCs are in the range of U1000 to U1255, go to next step. If no DTCs are recorded, problem is intermittent.
  4. If DTC U1000 or U1255 is the only DTC displayed, diagnose affected DTC(s). See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  5. Turn ignition off. Disconnect scan tool from DLC. Check for poor connections at DLC ground terminals. Repair as necessary. If connections are okay, go to next step.
  6. Check for open in DLC signal return circuit. Repair as necessary. If circuit is okay, go to next step.
  7. Remove comb from SP201 splice connector. Check for poor connections at SP201. Check continuity between pin "A" and all other pins at SP201. Repair as necessary. If connections are okay, go to next step.
  8. Check DLC class 2 circuit for open or short in circuit. Repair as necessary. If circuit is okay, go to next step.
  9. Connect a jumper wire to each end of both Body Control Module (BCM) class 2 serial data circuits. Turn ignition on, with engine off. Using scan tool, attempt to communicate with BCM. If scan tool communicates with BCM, go to step  11. If scan tool does not communicate with BCM, go to next step.
  10. Turn ignition off. Disconnect BCM harness connectors C1 and C2. Check BCM class 2 circuits for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to battery negative voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  11. Leave jumper wires connected to BCM class 2 circuit. Connect another jumper wire to each end of PCM class 2 circuit. Turn ignition on, with engine off. Using scan tool, attempt to communicate with PCM. If scan tool communicates with PCM, go to step  13. If scan tool does not communicate with PCM, go to next step.
  12. Turn ignition off. Disconnect PCM harness connector C1. Check PCM class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  13. Remove jumper wire from PCM class 2 circuit. Connect jumper wire to the end of Transfer Case Shift Control Module (TCSCM) control module class 2 circuit. Turn ignition on, with engine off. Using scan tool, attempt to communicate with TCSCM. If scan tool communicates with TCSCM, go to step  15. If scan tool does not communicate with TCSCM, go to next step.
  14. Turn ignition off. Disconnect TCSCM harness connector containing the TCSCM class 2 circuit. Check TCSCM class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  15. Disconnect jumper wire from TCSCM class 2 circuit. Connect jumper wire to end of Vehicle Interface Unit (VIU) class 2 circuit. Turn ignition on, with engine off. Using scan tool, attempt to communicate with VIU. If scan tool communicates with VIU, go to step  17. If scan tool does not communicate with VIU, go to next step.
  16. Turn ignition off. Disconnect VIU harness connector. Check VIU class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  17. Remove jumper wire from VIU class 2 circuit. Connect jumper wire to the end of EBCM class 2 circuit. Turn ignition on, with engine off. Using scan tool, attempt to communicate with EBCM. If scan tool communicates with EBCM, go to step  19. If scan tool does not communicate with EBCM, go to next step.
  18. Turn ignition off. Disconnect EBCM harness connector C1. Check EBCM class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to battery positive voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  19. Remove jumper wire from EBCM class 2 circuit. Connect jumper wire to the end of inflatable restraint Sensing and Diagnostic Module (SDM) class 2 circuit. Turn ignition on, with engine off. Using scan tool, attempt to communicate with SDM. If scan tool communicates with SDM, go to step  21. If scan tool does not communicate with SDM, go to next step.
  20. Turn ignition off. Disconnect SDM harness connector. Check SDM class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  21. Remove jumper wire from SDM class 2 circuit. Connect jumper wire to the end of Instrument Panel Cluster (IPC) class 2 circuit. Turn ignition on, with engine off. Using scan tool, attempt to communicate with IPC. If scan tool communicates with IPC, go to step  23. If scan tool does not communicate with IPC, go to next step.
  22. Turn ignition off. Disconnect IPC harness connector. Check IPC class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to battery positive voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  23. Remove jumper wire from IPC class 2 circuit. Connect jumper wire to the end of Memory Seat Module (MSM). Turn ignition on, with engine off. Using scan tool, attempt to communicate with MSM. If scan tool communicates with MSM, go to step  25. If scan tool does not communicate with MSM, go to next step.
  24. Turn ignition off. Disconnect MSM harness connector C1. Check MSM class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to battery positive voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to step  29.
  25. Remove jumper wire from MSM class 2 circuit. Connect jumper wire to the end of Driver Information Center (DIC). Turn ignition on, with engine off. Using scan tool, attempt to communicate with DIC. If scan tool communicates with DIC, go to step  31. If scan tool does not communicate with DIC, go to next step.
  26. Turn ignition off. Disconnect DIC harness connector C1. Check DIC class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to battery positive voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to next step.
  27. Remove jumper wire from DIC class 2 circuit. Connect jumper wire to the end of Electronic Climate Control (ECC) module. Turn ignition on, with engine off. Using scan tool, attempt to communicate with ECC module. If scan tool communicates with ECC module, go to step  31. If scan tool does not communicate with ECC module, go to next step.
  28. Turn ignition off. Disconnect ECC module harness connector. Check ECC module class 2 circuit for short to battery negative voltage or short to battery positive voltage. Turn ignition on, with engine off when testing for short to battery positive voltage. Repair as necessary. After repairs, go to step  31. If circuit is okay, go to next step.
  29. Check for poor connections at class 2 circuit of module that is not communicating. Repair as necessary. After repairs, go to step  31. If connections are okay, go to next step.
  30. Replace module which is not communicating. After replacing affected module, go to next step.
  31. Reconnect all modules and connectors. Connect scan tool. Turn ignition on, with engine off. Wait 10 seconds. Scan tool may require a power up reset before communication will occur due to a short on the class 2 circuit. Turn off or disconnect scan tool prior to performing this test. Using scan tool, select display DTCs function for each module. Record all displayed DTCs and DTC status. If DTCs are recorded, go to next step.
  32. Diagnose affected DTCs. After repairs, clear DTCS using scan tool.
scientia non olet · About LEMON Manuals