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Home >> GMC >> 1998 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 22 (Transfer Case - Diagnosis - New Venture 246) >> DTC Tests >> DTC C0327: Encoder Circuit Malfunction >> Testing

DTC C0327: Encoder Circuit Malfunction: Testing

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  1. If ATC system check was performed, go to next step. If system check was not performed, see ATC SYSTEM CHECK  .
  2. Turn ignition off. Connect scan tool to DLC. Turn ignition to run position (engine off). Using scan tool, record all freeze frame and failure records. Turn ignition off. Disconnect transfer case connectors. Turn ignition to run position (engine off). Using a DVOM, measure voltage between ground and Light Green/Black wire terminal at transfer case connector. See WIRING DIAGRAMS  . If voltage is 7-9 volts, go to next step. If voltage is not 7-9 volts, go to step 11).
  3. Using a DVOM, measure voltage between ground and Brown/White wire terminal at transfer case connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to step 20).
  4. Using a DVOM, measure voltage between ground and Dark Blue/White wire terminal at transfer case connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to step 23).
  5. Using a DVOM, measure voltage between ground and Yellow/Black wire terminal at transfer case connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to step 26).
  6. Using a DVOM, measure voltage between ground and Red/White wire terminal at transfer case connector. See WIRING DIAGRAMS  . If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to step 29).
  7. Connect self-powered test light between ground and Black/White wire terminal at transfer case connector. If test light is on, go to next step. If test light is off, go to step 19).
  8. Connect 3 jumper wires from Dark Blue/White wire terminal, Yellow/Black wire terminal and Brown/White wire terminal to Black/White wire terminal. Turn ignition to run position (engine off). Using scan tool, read encoder gear position. If gear position is 4WD, go to next step. If gear position is not 4WD, go to step 10).
  9. Replace motor/encoder. See REMOVAL & INSTALLATION  . When replacement is complete, go to step 44).
  10. Replace ATC control module. See REMOVAL & INSTALLATION  . When replacement is complete, go to step 44).
  11. If voltage in step 2) was more than 9 volts, go to next step. If voltage was less than 9 volts, go to step 14).
  12. Turn ignition off. Disconnect ATC control module connector C1. Turn ignition to run position (engine off). Using a DVOM, measure voltage between ground and Light Green/Black wire terminal at transfer case connector. If voltage is more than .5 volt, go to next step. If voltage is less than .5 volt, go to step 10).
  13. Locate and repair short to voltage in Light Green/Black wire circuit. When repair is complete, go to step 44).
  14. Turn ignition off. Disconnect ATC control module connector C1. Connect self-powered test light between ground and Light Green/Black wire terminal at transfer case connector. If test light is on, go to next step. If test light is off, go to step 16).
  15. Locate and repair short to ground in Light Green/Black wire circuit. When repair is complete, go to step 44).
  16. Connect jumper wire between ground and Light Green/Black wire terminal F13 at ATC control module connector C1. See WIRING DIAGRAMS  . Connect self-powered test light between ground and Light Green/Black wire terminal at transfer case connector. If test light is on, go to step 10). If test light is off, go to next step.
  17. Locate and repair open in Light Green/Black wire circuit between ATC control module and transfer case connectors. When repair is complete, go to step 44).
  18. Turn ignition off. Disconnect ATC control module connector C1. Connect jumper wire between ground and Black/White wire terminal at ATC control module connector C1. Connect self-powered test light between ground and Black/White wire terminal at transfer case connector. If test light is on, go to step 10). If test light is off, go to next step.
  19. Locate and repair open in Black/White wire circuit between ATC control module and motor/encoder connectors. If no open is found, replace ATC control module. When repair or replacement is complete, go to step 44).
  20. If voltage in step 3) was more than 6 volts, go to next step. If voltage was less than 6 volts, go to step 32).
  21. Disconnect ATC control module connector C1. Using a DVOM, measure voltage between ground and Brown/White wire terminal at transfer case connector. If voltage is zero, go to step 10). If voltage is more than zero, go to next step.
  22. Locate and repair short to voltage in Brown/White wire circuit. When repair is complete, go to step 44).
  23. If voltage in step 4) was more than 6 volts, go to next step. If voltage was less 6 volts, go to step 34).
  24. Disconnect ATC control module connector C1. Using a DVOM, measure voltage between ground and Dark Blue/White wire terminal at transfer case connector. If voltage is zero, go to step 10). If voltage is more than zero, go to next step.
  25. Locate and repair short to voltage in Dark Blue/White wire circuit. When repair is complete, go to step 44).
  26. If voltage in step 5) was more than 6 volts, go to next step. If voltage was less than 6 volts, go to step 36).
  27. Disconnect ATC control module connector C1. Using a DVOM, measure voltage between ground and Yellow/Black wire terminal at transfer case connector. See WIRING DIAGRAMS  . If voltage is zero, go to step 10). If voltage is more than zero, go to next step.
  28. Locate and repair short to voltage in Yellow/Black wire circuit. When repair is complete, go to step 44).
  29. If voltage in step 6) was more than 6 volts, go to next step. If voltage was less than 6 volts, go to step 38).
  30. Disconnect ATC control module connector C1. Using a DVOM, measure voltage between ground and Red/White wire terminal at transfer case connector. If voltage is zero, go to step 10). If voltage is more than zero, go to next step.
  31. Locate and repair short to voltage in Red/White wire circuit. When repair is complete, go to step 44).
  32. Turn ignition off. Disconnect ATC control module connector C1. Connect self-powered test light between ground and Brown/White wire terminal at transfer case connector. If test light is on, go to next step. If test light is off, go to step 40).
  33. Locate and repair short to ground in Brown/White wire circuit. When repair is complete, go to step 44).
  34. Turn ignition off. Disconnect ATC control module connector C1. Connect self-powered test light between ground and Dark Blue/White wire terminal at transfer case connector. If test light is on, go to next step. If test light is off, go to step 41).
  35. Locate and repair short to ground in Dark Blue/White wire circuit. When repair is complete, go to step 44).
  36. Turn ignition off. Disconnect ATC control module connector C1. Connect self-powered test light between ground and Yellow/Black wire terminal at transfer case connector. If test light is on, go to next step. If test light is off, go to step 42).
  37. Locate and repair short to ground in Yellow/Black wire circuit. When repair is complete, go to step 44).
  38. Turn ignition off. Disconnect ATC control module connector C1. Connect self-powered test light between ground and Red/White wire terminal at transfer case connector. If test light is on, go to next step. If test light is off, go to step 43).
  39. Locate and repair short to ground in Red/White wire circuit. When repair is complete, go to step 44).
  40. Locate and repair open in Brown/White wire circuit. If no open is found, replace ATC control module. When repair or replacement is complete, go to step 44).
  41. Locate and repair open in Dark Blue/White wire circuit. If no open is found, replace ATC control module. When repair or replacement is complete, go to step 44).
  42. Locate and repair open in Yellow/Black wire circuit. If no open is found, replace ATC control module. When repair or replacement is complete, go to step 44).
  43. Locate and repair open in Red/White wire circuit. If no open is found, replace ATC control module. When repair or replacement is complete, go to next step.
  44. Turn ignition off. Reconnect all disconnected components. Set parking brake. Start and run engine at idle. Shift transmission to "N" position. Shift transfer case between all modes, allowing time between each mode shift for transfer case to complete shift request. Using scan tool, select "Specific DTC" and enter DTC C0327. If test runs and passes, system is functioning properly. If test does not run and pass, repeat test from step 1).
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