Well my saga for the Passlock has finally ended, No I didn't get rid of the Malibu. I fixed it, cost was around 100 bucks, and it should be permanent or at least for another 5 years.
First I was having intermittent failures, similar to those posted elsewhere on this and other newsgroups. I went to a very experienced automotive electrician and got detailed schematics of the Passlock or Passkey system used in ALL GM vehicles from 1998 to 2005.
There is an optional system that uses a coded key with a chip resistor in it. Look at your key and see if it has a number or # stamped on it, that and only that key will work.
Mine is a non coded key, or a standard passkey or passlock II system. The key actuates a pair of magnets that pass in the vicinity of a pair of Hall-effect sensors, basically a pair of transistor switches that use a magnetic field as a turn on junction for them. They are each attached to a precision resistor that drops the voltage on the yellow (data) wire, referenced to the black (ground) wire. The data line carries about 5.5 volts normally with the key off, when my key went to start that voltage dropped to 2.088 volts and stayed at that voltage until the key was taken to off. The next start cycle it repeated. A no-start (crank) cycle was 4-5 volts, a tamper was >2.2 volts or <1.8 volts and would cut off the engine after a few seconds.
I measured the voltage then cut the yellow wire after noting the correct START sequence, i.e. the engine started. When I cut the yellow wire the engine was not running but I made sure the voltages were correct, I put the shifter in "R" and did the "START" sequence and checked the voltage before I cut the wire. The "Theft System" annunciator came on just like it is supposed to. I then measured the resistance from the yellow wire on the ignition switch to the black wire and found 1808 ohms, NOTE this is my value yours WILL be different, there are thousands of combinations. I then when to my local Radio Shack and got the necessary resistor to substitute for the above resistance from the hall-effec sensors. I then slid a piece of heat shrink tubing (electrical tape will work) over the yellow wire to the BCM and soldered the resistor to the yellow wire and to the black wire. Now my passkey is permanently set to good data.
Do not try to unplug the three wires from the lock assembly, you will ruin the connector and possibly the lock. The lock must be partially removed to unplug the connector, easy enough, turn you key to run and press the square metal button on the bottom of the ignition switch the whole tumbler and key will slip out, remove it about 1/2 inch then disconnect the connector. You can put the correct resistor between the yellow and black pins , then tape the connector and resistor up, and slide the lock back in.
Well on with my saga, I did the above resistor modification after some experiments to see what values did what, I wrote everything down.
About a week after I did the modifications I noted the vehicle was cranking again and not starting, being the technician I am I started noting symptoms. Turn key all idiot lights light, go to start display goes blank, NO START. Turn key idiot lights stay on vehicle starts, turn key idiot lights stay on then blink off no start. Tells me the ignition switch is FUBAR (Fu--ed up beyond all recognition) anyhow I replaced the ignition switch with a brand new ACdelco part an lo-and-behold it worked perfectly, hence the $100 cause that's what the switch goes for. The part # is ACD1432D, use only this part. You have to take out the instrument cluster to put it in but it takes about 20 minutes, half dozen body clips and 2 screws above the instrument cluster trim piece, 9 hex head screws, (6 if you don't pull the radio) but it makes it easier to get two hands in there.
pat