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Lighting System Diagnostic System Check

  1. Connect scan tool to Data Link Connector (DLC). If scan tool powers up, go to next step. If scan tool does not power up, go to SCAN TOOL DOES NOT POWER UP  .
  2. Turn ignition on. Attempt to establish communication with Powertrain Control Module (PCM), Platform Zone Module (PZM) and instrument Panel Cluster (IPC). If scan tool communicates with all modules listed, go to next step. If scan tool does not communicate with all modules listed, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  .
  3. Select display DTCs function for each module listed in step  2 . If any DTCs are set for any module listed, go to next step. If no DTCs are set for any module listed, attempt to diagnose lighting system by symptom.
  4. If scan tool does not display and DTCs that begin with "U", go to next step. If scan tool displays any DTCs that begin with "U", go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  .
  5. If scan tool displays DTC B1552, B1556, B1558, B1982 or B1983 for PZM, go to DIAGNOSTIC TESTS  . If scan tool does not display DTC B1552, B1556, B1558, B1982 or B1983 for PZM, go to next step.
  6. If scan tool displays DTC B1552, B1557, B1981, B1982 or B1983 for IPC, go to SELF-DIAGNOSTIC SYSTEM in ANALOG INSTRUMENT PANELS - ELDORADO article. If scan tool does not display B1552, B1557, B1981, B1982 or B1983 for IPC, go to next step.
  7. If scan tool displays DTC P1820, P1822, P1823 or P1825, go to appropriate SELF-DIAGNOSTIC SYSTEM article in ENGINE PERFORMANCE. If scan tool does not display P1820, P1822, P1823 or P1825, go to next step.
  8. If scan tool displays DTC B1910 or B1911, go to SELF-DIAGNOSTIC SYSTEM in GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If scan tool does not display DTC B1910 or B1911, diagnose and repair lighting system as necessary. See BACK-UP LIGHTS, HEADLIGHT SYSTEMS & DAYTIME RUNNING LIGHTS, EXTERIOR LIGHTS or ILLUMINATION/INTERIOR LIGHTS article.
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