PASS-Key® II is a registered trademark of the Delco Electronics Corporation.

When a key is inserted in the ignition, the contacts located in the ignition cylinder contact a resistor pellet located in the key. The instrument cluster (IPC) measures the resistance of the key pellet. The IPC then compares this value to a value stored in the IPC's memory. If the values match, the IPC sends a class 2 message to the powertrain control module (PCM). The PCM then enables the starter system to operate. If the values do not match, the IPC does not send a starter system enable class 2 message to the PCM. The IPC does not enable the starter system for approximately 3 minutes.

If the ignition switch is turned to the RUN position anytime during the system disable interval, the IPC disregards the key pellet value until the 3 minute system disable interval is complete (even if the correct key pellet value was used).

After approximately 3 minutes, the IPC measures the key pellet resistance. The IPC compares this value to the one stored in the IPC's memory. If the values match, the IPC performs the system enable function (see above). If the values do not match, the IPC performs the system disable functions again (see above).

If the IPC is unable to measure the key pellet resistance (due to a damaged or missing pellet), the IPC does not perform the system disable functions. Use a readable key with the correct resistance value in order to start the vehicle.

The ignition key for the vehicles equipped with the PASS-Key® II system consists of a typical square ignition key blank and a resistor pellet. The PASS-Key® II ignition key has the same mechanical key cuts of a non PASS-Key® II ignition key. Do not service the key blank and the resistor pellet separately. There are 15 different ignition key assemblies, each with a different key pellet resistance value.

The ignition lock cylinder used with the PASS-Key® II system contains a set of electrical terminals used in order to contact the resistor in the ignition key. The wire routing for the contacts inside the steering column is very critical. When servicing the lock cylinder, maintain proper wire routing. When replacing a ignition lock cylinder, make new keys which match the PASS-Key® II key code of the PASS-Key® II system and the mechanical cut of the new lock cylinder.

The instrument cluster (IPC) contains the software for controlling the PASS-Key® II system. The IPC monitors the following components:

The IPC also sends a starter enable message to the powertrain control module (PCM) via the class 2 serial data line.

The key-in-ignition input CKT 80 (LT GRN) is used in order to wake up the instrument cluster (IPC) when a key is inserted into the ignition lock cylinder (ignition switch). When the IPC wakes up, the IPC measures the key pellet resistance value on the ignition key resistor input CKT 1073 (WHT/BLK).

The ignition key resistor input CKT 1073 (WHT/BLK) is used by the instrument cluster (IPC) in order to measure the key pellet resistance.

The theft deterrent relay is controlled by the Powertrain Control Module via the starter enable output CKT 447 (YEL). If the IPC measures the correct key pellet resistance value, the IPC sends a message on the class 2 serial data line to the Powertrain Control Module to ground the theft deterrent relay. The relay is energized, if the ignition switch is in the start position and the gear selector is in park or neutral position.

The powertrain control module (PCM) monitors the class 2 serial data line for the starter enable message from the instrument cluster (IPC). If the starter enable message is not present, the PCM does not enable the starter system during the engine crank. If the message is present, the PCM enables the starter system. This condition allows the engine to start during the engine crank.