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DTC B1440: Power Mode Master Input Circuits Mismatch: Testing

  1. Perform diagnostic system check for system exhibiting symptoms. See DIAGNOSTIC SYSTEM CHECK INDEX  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. Using scan tool, monitor Body Control Module (BCM) DATA DISPLAY ignition 0, ignition 1 and ignition accessory inputs. If scan tool indicates that all inputs are inactive, go to next step. If scan tool does not indicate that all inputs are inactive, go to step  7.
  3. Turn ignition switch to ACC position. Using scan tool, monitor BCM DATA DISPLAY ignition 0, ignition 1 and ignition accessory inputs. If scan tool indicates that inputs ignition 0 and ignition accessory are inactive, go to next step. If scan tool does not indicate that inputs ignition 0 and ignition accessory are inactive, go to step  9.
  4. Turn ignition switch to RUN position. Using scan tool, monitor BCM DATA DISPLAY ignition 0, ignition 1 and ignition accessory inputs. If scan tool indicates that all inputs are active, go to next step. If scan tool does not indicate that all inputs are active, go to step  9.
    5. NOTE: Engine may start in this step. Turn engine OFF immediately after reviewing the input data.
  5. Turn ignition switch to RUN position. Using scan tool, monitor BCM DATA DISPLAY ignition 0, ignition 1 and ignition accessory inputs. If scan tool indicates that ignition 0 input is inactive and ignition accessory input is active, go to next step. If scan tool indicates that ignition 0 input is inactive and ignition accessory input is active, go to step  9.
  6. In previous steps if any ignition switch input was active when not called for, go to next step. In previous steps if any ignition switch input was not active when called for, go to step  12.
  7. Disconnect ignition switch 7-pin harness connector. Ignition switch located on steering column. Using scan tool, monitor BCM DATA DISPLAY ignition 0, ignition 1 and ignition accessory inputs of suspect circuits. If scan tool indicates that any input is active, go to next step. If scan tool does not indicate that any input is active, go to step  10.
  8. Disconnect all BCM harness connectors. BCM is located inside center console above center console fuse block. Check for short to voltage in ignition switch input circuits to BCM. See WIRING DIAGRAMS . If problem is found, repair as necessary and go to step  15. If no problem is found, go to step  12.
  9. Disconnect ignition switch 7-pin harness connector. Ignition switch is located on steering column. Install a fused (3-amp) jumper wire between suspect circuit(s) and ignition switch harness connector terminal "B" (Orange wire). See Fig 1. Using scan tool, monitor BCM DATA DISPLAY ignition 0, ignition 1 and ignition accessory inputs of suspect circuits. If scan tool indicates that suspect circuit is now active, go to next step. If scan tool does not indicate that suspect circuit is active, go to step  11.
  10. Check for poor, loose or corroded terminals in ignition switch harness connector. If problem is found, repair as necessary and go to step  15. If no problem is found, go to step  13.
  11. Disconnect all BCM harness connectors. BCM is located inside center console above center console fuse block. Check for short to ground in ignition switch input circuits to BCM. See WIRING DIAGRAMS . If no problem is found, go to next step. If problem is found, repair as necessary and go to step  15.
  12. Check for poor, loose or corroded terminals in BCM harness connectors. If problem is found, repair as necessary and go to step  15. If no problem is found, go to step  14.
  13. Replace ignition switch. See STEERING COLUMN SWITCHES - AZTEK article. After repairs are made, go to step  15.
  14. Replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION. After repair are made, go to next step.
  15. Reconnect any disconnected component. Using scan tool clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay. If DTC resets, go to step  2.
Fig 1: Identifying Ignition Switch Harness Connector Terminals
G00066106Courtesy of GENERAL MOTORS CORP.
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