Circuit Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The body control module (BCM) supplies a 5 volt signal and a ground circuit for the PASS-Key® system. This allows the BCM to detect PASS-Key® resistance values. Inserting the PASS-Key® (with resistor pellet) in the ignition lock cylinder completes the PASS-Key® circuit. Contacts in the ignition lock cylinder mate with the pellet contacts. The BCM compares the resistance value of the key pellet to the valid resistance programmed into the BCM. If the proper resistance value is read, the BCM allows the following functions to occur:

The theft deterrent relay to energize.
The steering column to unlock.
The BCM sends a message through the serial data line to the powertrain control module (PCM) to allow fuel enable processing to occur.

When a BCM is replaced, the BCM must be programmed to accept the resistance value of the existing vehicle keys in order to allow PASS-Key® operation. When the BCM is replaced, the service replacement BCM is programmed to accept the first PASS-Key® resistance value detected. If the BCM is unable to detect a valid PASS-Key® resistance value, the BCM will never end the programming sequence and DTC B2735 will set.