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11-28-2007, 05:24 AM | #1 | |
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94 Buick LeSabre No Security Light,Vats Kills engine after start
I hope that someone has had better luck than me with this VATS. I recieved this car from a guy who wanted to drive it daily, Seem his Father in law was not able to drive any longer. The car had not been started in a year. I cleaned eveything up(inside and outside the car and gave it a tune up. My freind started driving it and it would occationaly start then die.After 20 minute or so,it would eventuly stay running.Found that the wires on the ecm connector (red) were cut to disable CEL.After resoldering the wires back to their correct configurtion, the CEL comes on but I don't get a security light.The tumbler assy is bad so I cut wiring at the column and inserted the correct resistor for the vats(according to a web site that listed the resistance for all the GM keys. Is the VAts unit itself bad and Where is it. I check the bulb in the instrument cluster an foud it to be good. I heard it was buried in the dash deep.I've tried another ecm and no luck. Any help would be appreciated. Thanks
Last edited by Ratt643; 11-29-2007 at 11:41 AM. |
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11-28-2007, 08:51 PM | #2 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
the anti-theft module is right above the glove box and the box is easy to remove. had a vats problem coding on my sons 1994 lesabre last spring. check out the thread in tips and maintenance for lesabre, it's titled"diagnostic tips for vats" by steven david . around the same time i was working my problem , another member reported a shorted injector as the cause to his same problem
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11-28-2007, 09:10 PM | #3 | ||
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
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11-29-2007, 09:01 AM | #4 | ||
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
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11-29-2007, 09:06 AM | #5 | ||
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
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11-29-2007, 09:19 PM | #6 | ||
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
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If the resistance is correct, either from the bypass resistor or key, the TDM will send a Pulse-Width Modulated signal to the PCM, and then the PCM will enable the fuel injectors. The TDM also operates the Start Enable Relay (SER) that allows power to reach the starter solenoid when the key is turned to the START position. If the TDM does not recognize the key or bypass resistor, it decides a theft attempt is in progress and it will go into anti-theft mode. In this mode, the TDM will: 1) Turn on the “Security” warning light on the instrument panel. (This may or may not happen with a bypass resistor installed) 2) Prevent starter operation by not turning on the Start Enable Relay. 3) Send a signal to the PCM telling it to disable the fuel injectors. 4) Disable the key recognition circuit for three minutes. As you can see, the TDM controls two functions when you attempt to start. First, it sends a pulse width modulated (PWM) signal to the PCM to allow injector pulse and then it allows the start enable relay to energize. These two functions happen almost simultaneously. It would be very unusual for the TDM module itself to fail – except perhaps if it has been subjected to a “voltage spike” or other problem that has occurred within the vehicle’s wiring. If that were the case, the TDM would not energize the Start Enable Relay.
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11-30-2007, 04:11 AM | #7 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
Is the TDM seperate from the VATS? If it is, where is it located? I never have had the security light come on even before I installed the resistor. I wouldn't put it past this car that it had the battery cable pulled while running(voltage spike). I checked the security bulb in the instrument cluster and it is ok. What next?
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12-01-2007, 03:25 AM | #8 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
Ignore the VATS system. Your problem is not that. You have the same symptoms that almost every stall post from that era car has. The common faults to cause it are: crank sensor, ignition module, MAF sensor, and possibly fuel pump/pressure. Those are the main ones. Other things can be involved as well. As HotZ says, VATS will never stall your car once running.
Since you have the check engine light, check your engine codes (paperclip on spots A & B on the under-steering-column-on-black-plastic-under-dash-shield ALDL wiring harness connector--turn key to run (but NOT start) and watch the light flashes beyond the "1" "2" which indicates the system is working and note the codes). |
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12-01-2007, 07:24 AM | #9 | ||
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
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The Vehicle Anti Theft System (VATS) was first installed on the 1985 Corvette. The Personal Anti-Theft Security System (PASSkey) replaced VATS in 1988, and while there are some differences, VATS and Passkey I and II all work the same way. There is no radio communication involved; the system merely looks for the ignition key’s unique electronic signature. The older Passkey systems all have a pellet imbedded in the ignition key that communicates with the Theft Deterrent Module (TDM). Passkey II does not use a seperate TDM (module) so the same security functions are built into the Body Control Module (BCM). Passkey III and the newer Passlock systems were introduced in 1998, but the earlier systems weren’t completely phased out until 2003. Passkey III uses radio communications between two modules. There is a small chip in the ignition key called a transponder. When the key is inserted into the ignition switch it sends a code to the vehicles computer through a receiver coil mounted to the barrel. Once the computer has identified it as a valid key, it enables the starter and fuel management systems. Are you absolutely sure that the loss of injector pulse is the reason for the engine stall? Have you used noid lights for testing injector pulse?
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12-01-2007, 02:56 PM | #10 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
I have tried to download codes but my scantool will not link. I tried my friends AutoXRay and it will not link. I ordered a remanufactered PCM and installed it, still will not link. I have not tried the injector pulse but will. I have replaced ignition module, MAF ,checked fuel pressure and regulator.Charging system is charging 14 volts. Have not tried crankshaft position sensor.Still wonder if one of the injectors is shorted out. It sux being half way around the world and just now get some more idea's. Oh well, be going home on Friday and will start to check car. Keep those thoughts and ideas coming!
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12-01-2007, 08:20 PM | #11 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
You need a scanner that will link to a 94-95 OBD1.5 ECU. Generic scanners will not connect. You can use an Actron CP9145 or CP9150. Check with your local shops to see if anyone has a scanner capable of reading the 94-95 OBD1.5 ECU.
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12-02-2007, 07:11 PM | #12 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
to hotZ28; your right , it was not the vats system that caused a start then stall immediatly condition. it turned out to be the ECM , even though the code was for "security breach". I did explain that. but numerous posts at the time were pointing to the vats system as the answer
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12-03-2007, 02:25 AM | #13 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
Do you think the problem could be in the PROM? When I changed the ECM, I had to transfer the old PROM to the new ECM. Like I said, there was no change in the car, so reinstalled the old ECM.
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12-08-2007, 08:43 AM | #14 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
I used the old prom with a pcm from auto zone 90$. did you ever check the voltage from the anti- theft module? the 1994 lesabre seems to be a transition year for the obd and vats,creating a lot of confusion,so i'm trying to only relay past experience and not guess at answers. good luck!!!
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12-12-2007, 09:21 PM | #15 | |
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Re: 94 Buick LeSabre No Security Light,Vats Kills engine after start
Well, After finally returning home,I looked behind the dash above the glove box and saw a green connector just hanging there.I then went to a salvage yard and looked at another LeSabre and found a small box connected to it. I bought the box and got the resistance value from the key. A trip to Radio Shack netted me the proper value resister for that Theft Deterent Module.
I returned home, connected the TDM and the resister. Turned the key on, the securuity light came on and when started, it stayed running! I don't know how whoever worked on this thing before managed to make the car stay running without the TDM! Thanks to all of you for help on this part, now I have to start a new post for another problem. Thanks again! |
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