Circuit Description

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

NOTE: CRANK relay may also be referred to as theft deterrent relay.

When ignition switch is turned from LOCK or OFF position to RUN position, 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 correct, BCM will use Class 2 serial data line to send an enable password to PCM. PCM will then energize CRANK relay and allow fuel delivery to engine.

When BCM is replaced, it must be programmed to accept resistance value of existing vehicle keys to allow PASS-Key(R) II operation. New BCM is programmed to accept first PASS-Key(R) II resistance value that it detects.

DTC B3031 will set when BCM is unable to detect a valid PASS-Key(R) II code during programming procedure due to other malfunctions which are present (an open or short circuit). BCM will not end programming sequence. BCM will send a message to PCM to enable CRANK relay and to allow fuel delivery to engine. When DTC B3031 is set, BCM will send a message to instrument panel to turn on SECURITY indicator.

A current DTC B3031 will clear from memory when BCM detects a valid PASS-Key(R) resistance value on PASS-Key(R) signal circuit. A history DTC B3031 will clear after 100 consecutive ignition cycles if condition for setting DTC is no longer present. DTC will also clear when scan tool is used to clear DTCs.

If conditions for malfunction no longer exist, history DTC will clear after 100 consecutive ignition cycles. DTC B3031 will also clear when conditions no longer exist or scan tool is used to clear codes.

NOTE: A history DTC B3031 indicates BCM had previously entered and successfully completed programming mode. Using scan tool, clear DTCs and recheck system operation.

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.