GM Pass Lock II Relearn Procedure

Posted:

Pass Lock II is used on many GM vehicles from 1995-2005 and can be identified by a security light on the dash and by an ignition key with a “PK2” stamped on the metal part of the key where it meets the plastic end. There are some keys that may not have the “PK2” stamped on them and are also used for this system. These keys only function to turn a lock cylinder that houses a magnet in the center of the key cylinder assembly

(Figure 1) Pass Lock Figure 1.

When the lock cylinder is rotated in the crank mode it will travel far enough for the magnet to go past the sensing device allowing the sensor to send a signal to the security module.

The sensing device is a 3-wire Hall Effect sensor

(Figure 2) Pass Lock Figure2

that the security module feeds a referance ground and referance power on 2 of the wires. The 3rd wire is a 5V referance signal line from the security module that the sensor will pull to a certain level when the magnet passes the sensing device. The hall sensors each have their own unique end result value between 0.5-4.5 volts when pulling the 5V ref low and this value will be learned by the security module and kept in its memory. When the battery goes dead or a new hall sensor is replaced you will need to relearn the Pass Lock sensor value into the security module.

The learn procedure is as follows:

Turn the lock cylinder all the way to the crank mode so the magnet on the lock cylinder can travel pass the Pass Lock sensor. Now let go of the key so it can return to the run position. The 5 Volt line will now be pulled to a value below 5 volts and the security light may begin to start flashing or just remain on solid. Some vehicles may start up and stall or may not crank at all. You must leave the ignition key on for 10 minutes and place a battery charger on the battery if needed in case the battery is low on charge. After 10 minutes you will see the security light go out or just stop flashing and then go out. At this point you turn the key off for 5 seconds. After 5 seconds you turn the lock cylinder to the crank position again to repeat the same process .You must perform this process 3 times for a total of 30 minutes of wait time. On your 4th attempt the vehicle should start up and continue to run.

This procedure does not apply if the vehicle has a Pass Lock III system. This system can be identified by a Security module & antenna straddling the lock cylinder. The keys for the Pass Lock III system are also different in nature. They will have a “PK3” or a “+O” stamped on them. These keys are true immobilizor keys and have tiny chips imbedded in them. The Pass Lock III systems require a differ learn procedure.

Categories

Recent Posts

GM Pass Lock II Relearn Procedure

Posted: February 12, 2015

Disabling a Hybrid

Posted: February 12, 2015

Check out my book!

Preview Book

Choose Format

We're Proudly Affiliated With

Caution: Vehicle servicing performed by untrained persons could result in serious injury to those persons and others. Information contained in this website is intended for use by trained, professional auto repair technicians ONLY. This information is provided to inform these technicians of conditions which may occur in some vehicles or to provide information which could assist them in proper servicing of these vehicles. Properly trained technicians have the equipment, tools, safety instructions and know-how to perform repairs correctly and safely. If a condition is described, DO NOT assume that a topic covered in this website automatically applies to your vehicle or that your vehicle has that condition. Always refer to the applicable repair manuals, bulletins and other original equipment service information.

The ATOW Tech Man is a registered trade mark and can not be used or reproduced without written consent of Auto Tech On Wheels, Inc. All content found here is copyrighted and reproduction is forbidden without written consent of John Anello, Auto Tech On Wheels, Inc. All logos and brands are represented by their respecitve copyrights & trademarks.