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Twilight Photocell Test

  1. Turn on ignition. Enter diagnostics and select BCM data BD44. See COMPUTERIZED ENGINE CONTROLS section for proper procedure.
  2. Expose twilight photocell to bright sunlight or a very bright incandescent light. BCM display should be 15 or less. Cover twilight photocell with cardboard. BCM display should be 90 or more.
  3. If BCM display is more than 15 with light applied to photocell, check voltage at BCM electrical connector (with connector connected). Using a voltmeter, check for one volt or less at White/Dark Green wire. If voltage is incorrect, replace twilight photocell.
  4. If BCM display is less than 90 with photocell covered, repeat step 3) voltage test. Voltage at White/Dark Green wire should be 4 volts or more. If voltage is incorrect, replace twilight photocell.
  5. If voltage readings in steps 3) and 4) are correct, replace Body Control Module (BCM) and repeat tests to verify repairs.
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