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Home >> Buick >> 1998 >> Century Custom >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Module >> Diagnostic Tests >> DTC B2721: Pass-Key(R) II Detection Circuit (Out Of Range) >> Diagnostic Aids

Diagnostic Aids

  1. The following conditions may cause an intermittent: dirty or loose ignition cylinder key contacts, dirty key resistor pellet, incorrect PASS-Key(R), Intermittent open or short to ground in circuit No. 1073 (White/Black wire) or No. 1074 (Purple/White wire), or poor connections at BCM or ignition switch connector.
  2. If key resistor pellet is incorrect, there will be no BCM outputs to theft deterrent relay or PCM for about 3 minutes. If a key (even a proper PASS-Key(R)) is inserted or ignition is turned on again, 3-minute time-out period will reset. If battery is disconnected, time-out period will be reset when battery is reconnected. During this 3-minute period, the SECURITY warning indicator will flash when ignition switch is turned to ON position. After the 3-minute period, SECURITY warning indicator will stay on steady, and BCM will enter the theft deterrent re-learn mode.
  3. Though it is unlikely, DTC B2721 may set due to extremely hot or cold ambient temperatures. To eliminate this possibility, perform tests with vehicle and key at room temperature.
  4. Clean key resistor contacts thoroughly. Check for poor connections at BCM and ignition lock cylinder. A poor connection may cause an open, an incorrect PASS-Key(R) resistance or an intermittent malfunction.
  5. When ignition switch is in RUN position with steering column lock and ignition key cylinder connector C207 disconnected, DTC B2723 may set. After diagnosis and repair of DTC B2721 is complete, clear DTCs and perform BCM DIAGNOSTIC SYSTEM CHECK  .
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