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Home >> Oldsmobile >> 1998 >> Bravada >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Module >> Diagnosis & Testing >> DTC B1398: 5-Volt Reference Circuit High >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform TBC module diagnostic system check. See procedures in TBC MODULE DIAGNOSTIC SYSTEM CHECK  . After performing system check, go to next step.
    NOTE: Ensure DTC B1398 is a current code before proceeding with test.
  2. Turn ignition switch to RUN position. Using DVOM connected to ground, backprobe Purple TBC module harness connector terminal A4 (Gray wire). If voltage reading is not greater than 5.25 volts, DTC is intermittent. See DIAGNOSTIC AIDS. If voltage is greater than 5.25 volts, go to next step.
  3. Turn ignition off. Disconnect Purple TBC module harness connector. Check for good connection at harness connector terminal A4 (Gray wire). If connection is okay, go to next step. If connection is faulty, go to step 7).
  4. Reconnect Purple TBC module harness connector. Using scan tool, clear DTCs. Turn ignition off for 10 seconds. Turn ignition switch to RUN position. Check DTCs. If DTC B1398 is set as current code, go to next step. If DTC B1398 is not set as a current code, go to step 8).
  5. Turn ignition switch to RUN position. Using DVOM connected to ground, backprobe Purple TBC module harness connector terminal A4 (Gray wire). If voltage reading is 5.25 volts or greater, go to step 8). If voltage reading is not 5.25 volts or greater, go to next step.
  6. Replace TBC module. Program and perform TCM module relearn procedure. See procedures in TBC MODULE PROGRAMMING/RPO CONFIGURATION  and TBC/BCM RELEARN PROCEDURE  . After programming TBC module, go to step 13).
  7. Repair terminal connection. After repairs, go to step 13).
  8. Disconnect light sensor harness connector. Turn ignition off. Using DVOM, check for short to voltage in light sensor Gray wire circuit between sensor and TBC module. If circuit is shorted to voltage, go to step 10). If circuit is okay, go to step 11).
  9. Replace light sensor. After replacing sensor, go to step 13).
  10. Repair Gray wire circuit. After repairs, go to step 13).
  11. Check for short to voltage in White wire between TBC module and light sensor. If circuit is shorted, go to next step. If circuit is okay, go to step 9).
  12. Repair White wire circuit. After repairs, go to next step.
  13. Clear DTCs. After clearing DTCs, perform TBC module diagnostic system check. See TBC MODULE DIAGNOSTIC SYSTEM CHECK  .
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