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Test Description

NOTE: Numbers in list refer to circled numbers in diagnostic flow chart, see Fig 1 . For circuit identification, see Fig 2 .
  1. BCM data value BD43 displays twilight delay time. The normal range is 4 to 96%.
  2. Check to see if the open or grounded circuit reading is due to the circuit or the switch assembly. If the open or grounded circuit reading changes to a short to voltage reading after jumpering the switch assembly terminals, the BCM and wiring are OK.
  3. Measuring the voltage between CKT 705 (5 volts) and 271 will determine if CKT 271 is open or shorted to ground.
  4. Check to see if the short to voltage circuit reading is due to the circuit or the switch assembly. If a short to voltage reading changes to an open circuit reading after disconnecting the switch assembly, the BCM and wiring are OK.
Fig 1: DTC B120: Twilight Delay Switch Pot Circuit Diagnostic Flow Chart
G00133552Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying Twilight Delay Switch Pot Circuit
G00133553Courtesy of GENERAL MOTORS CORP.
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