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DTC B1971: Inadvertent Power Fault: Testing

NOTE: If DTC B1971 is a history code, problem may be intermittent. Wiggle wires while performing the following test.
  1. If BCM system check was performed, go to next step. If BCM system check was not performed, go to BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  2. Connect scan tool to DLC. Select DELAY INTERIOR LIGHTS from light test menu in SPECIAL FUNCTIONS. While observing scan tool, command DIL relay on and off by pressing on and off buttons on scan tool. If status changes with commanded state, go to next step. If status does not change with commanded state, go to step  4 .
  3. Check for poor connection at BCM 32-pin connector C2 terminal C3 (Brown/Purple wire). See Figure . Check Red wire for poor connections. Check all BCM power and ground circuits. See WIRING DIAGRAMS  . If faulty circuit is found, go to step  13 . If circuit is okay, go to BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  4. Disconnect multifunction relay module connector. See Figure . Using DVOM, check resistance between multifunction relay module terminals No. 5 (Red wire) and No. 7 (Brown/Purple wire). See Fig 1 . If resistance is infinite, go to step  6 . If resistance is not infinite, go to step  7 .
  5. Replace BCM. See BODY CONTROL MODULE (BCM)  under REMOVAL & INSTALLATION. Reprogram BCM. See PROGRAMMING  . Perform BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  6. Replace multifunction relay module. Perform BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  7. Disconnect BCM 32-pin connector C2. Using DVOM, check resistance between multifunction relay module terminal No. 7 (Brown/Purple wire) and BCM connector C2 terminal C3 (Brown/Purple wire). If resistance is less than 2 ohms, go to next step. If resistance is greater than 2 ohms, go to step  9 .
  8. Move DVOM lead from multifunction relay module terminal No. 7 to ground. If resistance is infinite, go to step  10 . If resistance is not infinite, go to step  11 .
  9. Repair open in Brown/Purple wire between BCM and multifunction relay module. Perform BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  10. Leave DVOM connected as specified in step  8 . Switch DVOM to DC volts scale. Record voltage reading. Turn ignition switch to ON position. Record voltage reading. If both voltage readings are less than one volt, go to step  13 . If both voltage readings are not less than one volt, go to step  12 .
  11. Repair short to ground in Brown/Purple wire between BCM and multifunction relay module. Perform BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  12. Repair short to battery in Brown/Purple wire between BCM and multifunction relay module. Perform BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
  13. Using DVOM, measure voltage between ground and multifunction relay terminal No. 5 (Red wire). If battery voltage is indicated, go to step  15 . If battery voltage is not indicated, go to next step.
  14. Repair open in Red wire. After repairs, go to next step.
  15. Use scan tool to clear DTCs. Recheck system operation. See BCM DIAGNOSTIC SYSTEM CHECK  under SYSTEM TESTS.
Fig 1: Identifying Multifunction Relay Connector Terminals
G99J08637Courtesy of GENERAL MOTORS CORP.
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