95 Lesabre Pass Key Problem

Have a 1995 Buick Lesabre that will start then immediately dies scanner says it has an invalid pass key.. Installed new cylinder & key from GM still same problem...Then replaced theft module from Gm and we still have the same problem... Does anyone know what else I can try..

Have a 1995 Buick Lesabre that will start then immediately dies scanner says it has an invalid pass key.. Installed new cylinder & key from GM still same problem...Then replaced theft module from Gm and we still have the same problem... Does anyone know what else I can try..

I thought that if your car did not read a valid key, then the starter would not turn over. If so, I wonder about the invalid pass key. Nevertheless, the likely cause of a bad pass key signal in your case is bad wiring. You already replaced the ignition cylinder and VATS module, so wiring is all that is left. But, I would bypass the VATS system instead of fixing the wiring. Why? You'd never need a key with a resistor again, and also you would never have the problem with a key wearing out again, and you could simply dupe your ignition key at Home Depot or Lowe's and use it without a resistor. How to do it?

I'll paste my answer to someone else's similar issue below:

The bypass is your easiest and best solution. First, use a voltmeter to determine the resistance of your key's resistor. Check this figure against the resistance chart in the link below and find the closest value. Next, go to radio shack and buy resistors that add to close to the exact resistance that your key should be. Next, solder each resister together to make a chain to match the resistance of your key. Next, remove your glove box. Now, there is a black box towards the left side of the opening under a ledge. This is the VATS control box. If you remove the wire harness, you want to cut the purple/white wire and the white/black wire about 6 to 8 inches from the box (or whatever gives you plenty of work room). To be sure, the wires are in positions B8 and B7 on the wiring harness. Now, solder the resistor you made to the two wires going into the wiring harness that you cut (leave the other ends of the wires you cut free--they don't go anywhere for all practical purposes anymore). Use that black heat shrink tubing for putting the resistors together and also for the finished resistors to wiring job (or just use black electrical tape). Now, put the black box back if you removed it, or just put the electrical wiring harness back if you did not. Test it now using your key to see if the car starts (and without any red security light). If it works, then you no longer need a key with a resistor. You can dupe the resistor key at Lowe's and use that new key if you wanted.

You can also use this page as a guide:

http://vats.likeabigdog.com/

Note that I suggest putting the wire in near the box behind the glove box, while the site linked suggests putting your resistor chain under the steering wheel. I think my solution is better for two reasons. One, the access is easier doing it my way. Second, the orange wires in question are very small and flimsy and could develop an open with too much fidgeting. Either way is the same thing as the two orange wires connect to the two wires I suggest you use and nowhere else.

Good advice [Spinney1]

The problem sounds exactly like the VATS system problem.
It is first suprising that it allows you to crank.
* Does the security light turn on?

But, if you dont have the proper key value to put in a like resistor your kindof stuck. You may try all 15 resistor settings with a potentiometer from Radio Shack.
Ohms Ref.: http://vats.likeabigdog.com/

* The VATS TDM (Theft Deterent Module) will allow a 10 second run of the engine but cuts off the fuel injection pulses if the key is wrong.
* Also it provides the ground side of the start relay so that when the start relay is energized by the start position it can find ground and trip the start relay to power the starter solenoid.
Theres two fuses involved... one in the underhood fuse block (4) and one in the relay center (8).

It is suprising that it allows you to crank.
* Does the security light turn on?
Otherwise.
The PCM must see a brief pulsing signal (Dark blue) (pulse code) from the TDM during a start attempt.
Somehow you should check for the pulses.. 50-60hz

TDM wires
Red and pink - wires to the TDM should be just a voltage in run and start.
DarkBlue - enables to the PCM to inject fuel. (Pulses)
Green - lights to your security indicator
Blk/Whites- are to ground.
Purple/white and white/black - is out to your key pellet.

If No pulses at start attempt then it will take troubleshooting backwards from there back to module and key circuit.
If Yes pulses at start attempt the PCM is suspect.

HOW IT WORKS INFO WEBPAGE
http://www.findarticles.com/p/articles/mi_m3102/is_6_124/ai_n14890664
http://www.motorage.com/motorage/article/articleDetail.jsp?id=169809 (http://www.motorage.com/motorage/article/articleDetail.jsp?id=169809).
Good Luck

Just to let everyone know I fixed the problem It seems that under some conditions the vats module has to relearn the key.. This is done by turning
the key to the on position and wait until the security/theft light goes out.
Do this three times and it relearns the module.. After that the car should start.

Great info.. Wonder how much $$ that cost you to learn to wait.

Thanks.

This is a great thread....I hope I never need it. :rofl:

Could somebody send me a picture of the purple and white wires going to the VATS system? I'm having trouble finding it in my 95 lesabre. I looked both under the drivers side kickpanel and in the area behind the glovebox.

Could somebody send me a picture of the purple and white wires going to the VATS system? I'm having trouble finding it in my 95 lesabre. I looked both under the drivers side kickpanel and in the area behind the glovebox.

Sorry but please check the date and do not resurrect an old thread. Best to start a new post and you can link to this thread for reference purposes. Thread closed.

Posting in Closed or Outdated Threads
Click here (http://www.automotiveforums.com/vbulletin/showthread.php?t=635166)