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Home >> Buick >> 2000 >> Regal GS >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Anti-Theft Systems >> Anti-Theft System >> Diagnostic Tests >> DTC B2957: Security System Sensor Data Circuit Low & DTC B2958: Security System Sensor Data Circuit High >> Circuit Description
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Circuit Description

PASS-Key(R) II detection circuit is completed when PASS-Key(R) II (with embedded resistor pellet) is inserted in ignition lock cylinder. When contacts in lock cylinder mate with contacts of resistor pellet, key detection circuit through White/Black wire and Purple/White wire is completed.

When ignition switch is turned from OFF position to RUN position, Body Control Module (BCM) applies a 5-volt reference voltage to White/Black wire. BCM then reads resistor pellet code, and compares stored resistor pellet code with ignition key resistor pellet code to verify a correct match. If BCM determines resistance value of key pellet is okay, BCM will use Class 2 serial data line to send an enable password to Powertrain Control Module (PCM). PCM will then energize theft deterrent relay and allow fuel delivery to engine.

DTC B2957 will set when voltage level of PASS-Key(R) input (White/Black wire) is low (indicating invalid resistance detected or a short to ground) during crank cycle or for one second anytime after engine has been started.

When DTC B2957 is set, BCM will send a message to instrument panel to turn on SECURITY warning indicator. If DTC is set during crank cycle, BCM will not send a message to PCM to enable theft deterrent relay and allow fuel delivery to engine (vehicle will exhibit a "no crank" condition). If DTC occurs later in ignition cycle, BCM will enter fail-enable mode. During subsequent engine starts, BCM will send a message to PCM to enable theft deterrent relay and to allow fuel delivery to engine.

If conditions for malfunction no longer exist, history DTC will clear after 100 consecutive ignition cycles. DTC B2957 will also clear when conditions no longer exist or scan tool is used to clear codes.

NOTE: If DTC B2957 is a history code, problem may be intermittent. Wiggle wires and key while performing the following test.
NOTE: When ignition switch is turned to RUN position with BCM disconnected, PCM-related DTC P1626 will be set. After BCM repair is completed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
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