LeSabre 97 - PassKey II/Flashing Security

Hello,

I am (trying) to help friend of mine who owns LeSabre 97. I've spent countless hours to untangle this puzzle, and now it has became sort of challenge to me.

Symptoms of the cars are "typical":

- "Security" light is Flashing
- Car won't crank

GM says for this:

- Bulb Flashes and Engine Does Not Start -

"If the "SECURITY" indicator flashes once per second and the engine does not start, this indicates that the PASS-Key II™ module sensed an open, a short or otherwise invalid (value matched none of the available 15 key codes) input from the ignition key resistor input. The PASS-Key II™ module does not start the disable timer during this operation mode. This operation mode could also be caused by malfunctioning power or ground circuits. Check that the ignition key is not damaged and refer to the diagnostic procedures in this section."

When I disconnect TDM (and/or when connect my 50Hz simulator) the car will crank, engine start for 2-3 sec., than die.

NOTE THIS: "value matched none of the available 15 key codes."

So true, bypassing method did not worked, I did not know this at the time. Than I build 50Hz signal simulator with LM555 timer and didn't work either. Than I found couple of TDMs at junkyard, half of hours procedure to reprogramming them with car's ECM all failed. TDM is there, connected to system, but it behaves like it has nothing to do with the system. It is "alienated" so to speak. Whatever I've done it did not have any effect. It just steadily flashing.

Then I went to path of the measuring resistance to ground. I disconnected and isolate each wire and the circuits connected to TDM and found nothing. A car's ECM appear to be fine, there is 5V when TDM is disconnected, but there is no 2.5V (which must be according to working theory) when TDM is connected. Here, I am referring to Terminal A3 of TDM, which goes to pin 55 of ECM.

http://autolib.diakom.ru/CAR/Buick/1997/LeSabre/SYSTEM%20WIRING%20DIAGRAMS/8745.pdf

So, there is no Grounding meaning, no voltage drop, and consequently no 50Hz PWM signal (somewhere I read it is proprietary GM signal) is coming out from TDM when cranking, therefore the engine ECM shut down injectors. Could it be the module itself is bad? On PassKey II the Ground (I think) is coming from Start Enable Relay which is connected to PNP (Park Neutral Position) switch, now wondering could it be culprit of this nightmare? But if this true, why isn't possible to install TDM from another vehicle? An author of this paper says it is possible:

http://www.search-autoparts.com/searchautoparts/data/articlestandard//motorage/292005/169809/article.pdf

"If a new BCM is installed, it will learn the correct commands from the original PCM if either control unit was ever used in another vehicle, they must be reprogrammed together..."

In few post some folks mentioned that by replacing BCM is the cure of the problem. This car doesn't have BCM, this year has something what is called MALL which appear to be predecessor of BCM. A diagram of the MALL is here:

http://autolib.diakom.ru/CAR/Buick/1997/LeSabre/SYSTEM%20WIRING%20DIAGRAMS/8746.pdf

While I am not going make any definitive conclusion about anything here because MALL is connected to PNP switch, seems to me it has nothing to do with TDM's function, and replacing MALL wouldn't do any good in my case.

Could it be Ignition Switch and PNP switch? But the car is quite willing to crank and fire up when necessary conditions are provided - 50Hz PWM signal is what's needed. Second thing, since I am "just" helping, I am quite unwilling to reassemble steering column.

By using the elimination method I am focused on that TDM's Ground. Could it be that all three TDMs are bad, and even my own 555 circuit isn't working? I, also, wonder about that programing thing. How do I make the module to became "friendly"?

Now, I am into this thing that's for sure, and more than likely in the "box thinking" mode, and don't see "outside" what might be obvious for those with more experience or simply putted I am doing something wrong. I know there is lot of questions and given "the nature of the beast" I do not expect miracle. However any comment, opinion, advice will be highly appreciated.

Thanks

I put all connectors and fuses back in its places and recharged battery. Still infamous flashing "Security" light!

These are readings/measurements that I got today. One thing is obvious: pin A4 and its voltage, or better said no-voltage.
It should be 12V on both side of PNP switch, when in P or N position.

44436

"Something" doesn't letting currency go trough this particular circuit,
be it Start Enable Relay, PNP switch, or bad wiring.

It should be 12V on both side of PNP switch, when in P or N position. Do you have 12v on both sides? If not, the PNP is the culprit. If you do have 12v, you have a wiring problem. I assume you would need 12v on A4 before the relearn procedure (shown below) would work.

1.Turn the ignition switch to START, then release it to
the ON position (the engine will not start).
2. The “Security” light should be ON. After 10 minutes,
it should turn OFF.
3.Turn the ignition switch OFF and after five seconds,
repeat steps 1 and 2.

When this procedure has been done three times, turn
the ignition switch OFF. The control units will exchange
the correct commands during the next start-up attempt.
If programming is not completed correctly, either there
will be no theft protection or the system will lock in antitheft
mode and the engine won’t start.Try the programming
procedure again. Note that this will not reprogram
key recognition, only the information transmitted on the
Class 2 data link.

In few post some folks mentioned that by replacing BCM is the cure of the problem. This car doesn't have BCM, this year has something what is called MALL which appear to be predecessor of BCM.

If the 'BCM' your referring to a "Body Control Module" a 1997 does have a BCM. It's under the dash behind the glove box. I have a GM BCM for a 97 lesabre new, in the box sitting right here in front of me. I bought it at the dealer but fixed the problem before it came in. It's not a "predecessor" it's a full fledged BCM.

Chris.

I have this problem few years ago on my 97 Lesabre.

Read this post, it might be the same problem
http://www.automotiveforums.com/vbul...d.php?t=339485

Read this post, it might be the same problem
http://www.automotiveforums.com/vbul...d.php?t=339485Sorry,this is not a valid link.

Wow, a lot of confusing statements here.....

When I disconnect TDM (and/or when connect my 50Hz simulator) the car will crank, engine start for 2-3 sec., than die.

How does it crank? If you disconnect the module, there is nothing grounding the starter enable relay.....or are you grounding terminal A5(ckt 625), in addition to attaching your signal generator with the key in crank position?

If this is what you are doing, and the vehicle dies after two seconds, the reason is because the signal you are generating is not equivalent to the fuel enable signal.....

These are readings/measurements that I got today. One thing is obvious: pin A4 and its voltage, or better said no-voltage.
It should be 12V on both side of PNP switch, when in P or N position.

Another confusing post....you said you were able to crank the vehicle.....did you measure this with just the key on?If yes, it will read zero.... if you disconnect harness at TDM, should read bat voltage, with key in crank position....if you ground the circuit, with key in crank position, vehicle should crank....

This car uses the PassKey II module, not the BCM.....

Do you have the original module back in the car? If yes, then I don't believe any programming is needed.....only time, I believe you have to do the 30 minute procedure, is if you lost the Master key, or if you are replacing the PassKey II module...

Did you EVER check the key circuit? Did you ever measure the resistance of the key......stick it in the cylinder......and get the SAME resistance reading at harness connecor B7 and B8?

the passkey module is not reprogrammable,like other modules.Whenever the module needs replaced or ignition key and tumblers have been replaced,a new virgin anti-theft module will be needed.once an anti-theft pass key module has learned a specific ignition key value it cannot be re written.
A new passkey module is already in a state called registration mode.when you install this virgin module it is ready to learn the new key ohmic value.
after installing a new passkey module,turn the key to the koeo position for 5 seconds and then after 5 seconds proceed to the crank mode.the engine should start.if the engine does not crank,note the security light.if the security light comes on for 5 seconds and then goes out the passkey module is reading the proper key value.suspect a bad starter enable relay or a convential starter circuit problem.if the security light stays on a fault has been detected.retrieve codes with a scan tool.
Get one from dealer and make sure box is not open.

TDM looks for learned voltage drop on one of the white wires from the key resistor pellet in the key.one wire out from tdm to key will have 5 volts and other will return a learned voltage drop value from key to tdm.disconnect the connector from the tdm and check resistance of these 2 wires with key in the ignition.now measure the ohmic value of the key resistor pellet outside the cylinder.the value of the resistance should vary 5-10 ohms.also wiggle key and turn steering wheel while key is in the cylinder while observing the ohmmeter to check contacts in the key cylinder.Should be steady value.usually a flashing light on a passkey2 system is an open in one of the 2 or both wires that run from key cylinder to tdm or dirty contacts or faulty key.hope this helps......do resistance tests above.Joe

Do not know why the link did not work..Anyways this happen to my 97 Lesabre about 5 years ago. No start (starter does not engage), SECURITY light flash. The problem was the tumbler could not read the resistor on the key. The cheapest was to add a resistor or replace the tumbler (more costly).
I fixed it by cutting the wires (2 white wires incase in ORANGE cover) and soldering a resisitor. The value of resistor is on the key, you'll need a ohm meter to read both sides of the key and just solder that value in. The wires are under the dash going from the steering column to a big connnector on the left-side. By doing this the secuitry is bypassed. Hope this helps.