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Test Description

NOTE: The following numbered steps refer to circled numbers on diagnostic chart. See Fig 1 . For circuit identification, see Fig 2 .
  1. BCM data value BD44 displays light level. The normal range is from 2 to 99%.
  2. Check to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to a shorted circuit reading after jumpering sensor terminals, BCM and wiring are OK.
  3. By applying a ground to various points in circuits, an open can be isolated by observing whether parameter display can be changed from open reading to shorted reading.
  4. Check to see if shorted circuit reading is due to circuit on sensor. If shorted circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are OK.
Fig 1: DTC B119: Twilight Photocell Circuit Diagnostic Flow Chart
G00072698Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying Twilight Photocell Circuit
G00072697Courtesy of GENERAL MOTORS CORP.