LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Vats system

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Old Sep 29, 2022 | 03:53 PM
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Vats system

I had a no crank no start issue and when I did the security light would come on on the dash with the Ignition like normal but then when I got to where I could crank the car and it actually turn over the security light stopped working on the dash altogether and now the fuel pump don't come on and I have no idea what to do
Old Sep 29, 2022 | 04:29 PM
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Re: Vats system

Sounds like the PCM might not be receiving the “fuel enable” signal from the VATS (PASS-KeyII) system.

What year is your car? There are subtle differences in the system, depending on the year of the car.

Here's an excellent article on how the PASS-KeyII system works, and troubleshooting it:

4th Gen LT1 F-Body Tech-PassKey/VATS
Old Sep 29, 2022 | 06:28 PM
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Re: Vats system

Originally Posted by Injuneer
Sounds like the PCM might not be receiving the “fuel enable” signal from the VATS (PASS-KeyII) system.

What year is your car? There are subtle differences in the system, depending on the year of the car.

Here's an excellent article on how the PASS-KeyII system works, and troubleshooting it:

4th Gen LT1 F-Body Tech-PassKey/VATS
it's a 94 z28 lt1
Old Sep 29, 2022 | 08:20 PM
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Re: Vats system

When you say “the SECURITY light stopped working …… altogether” do you mean it no longer lights up even during the 3 second bulb check when you turn the key to “RUN”?

And are you saying the fuel pump no longer primes for two seconds when you turn the key to “RUN”?
Old Sep 29, 2022 | 09:05 PM
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Re: Vats system

Originally Posted by Injuneer
When you say “the SECURITY light stopped working …… altogether” do you mean it no longer lights up even during the 3 second bulb check when you turn the key to “RUN”?

And are you saying the fuel pump no longer primes for two seconds when you turn the key to “RUN”?
Correct for both questions.
Old Sep 29, 2022 | 10:59 PM
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Re: Vats system

Do all the other dash warning lights come on in bulb check? If only the “SECURITY” light is totally inoperative, may be pointing to a problem with the theft deterrent module (DTM). That's what controls the SECURITY light.

But that doesn’t account for the fuel pump not priming. That is controlled by the PCM, at least on the initial turn of the key. After it primes for two seconds and shuts down the PCM is looking for the fuel enable signal from the TDM. It would have to be a partial failure of the TDM because is also sends a ground to the theft deterrent relay (TDR) that enables the starter.

http://shbox.com/1/pass_key.jpg

It's possible to scan the PCM for the code (DTC 46) that indicates the TDM is not sending the fuel enable system. If it’s a problem with the TDM not sending the fuel enable signal, there is a reasonably priced bypass module that can supply the signal to the PCM.
Old Sep 29, 2022 | 11:06 PM
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Re: Vats system

Originally Posted by Injuneer
Do all the other dash warning lights come on in bulb check? If only the “SECURITY” light is totally inoperative, may be pointing to a problem with the theft deterrent module (DTM). That's what controls the SECURITY light.

But that doesn’t account for the fuel pump not priming. That is controlled by the PCM, at least on the initial turn of the key. After it primes for two seconds and shuts down the PCM is looking for the fuel enable signal from the TDM. It would have to be a partial failure of the TDM because is also sends a ground to the theft deterrent relay (TDR) that enables the starter.

http://shbox.com/1/pass_key.jpg

It's possible to scan the PCM for the code (DTC 46) that indicates the TDM is not sending the fuel enable system. If it’s a problem with the TDM not sending the fuel enable signal, there is a reasonably priced bypass module that can supply the signal to the PCM.
yes all other lights come on except security and chech engine.
Old Sep 30, 2022 | 09:01 AM
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Re: Vats system

The PCM will also set a code for a faulty SES light. Time to scan for codes.
Old Sep 30, 2022 | 03:25 PM
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Re: Vats system

Originally Posted by Injuneer
The PCM will also set a code for a faulty SES light. Time to scan for codes.
all of this happened after I stuck a jack handle between my headers to tap on the starter cause I though the starter not turning was the cause of the starter solenoid going bad.
Old Sep 30, 2022 | 05:18 PM
  #10  
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Re: Vats system

Any possibility you shorted something and blew a fuse? One of the PCM grounds is on an engine block stud near the starter.
Old Sep 30, 2022 | 06:05 PM
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Re: Vats system

Originally Posted by Injuneer
Any possibility you shorted something and blew a fuse? One of the PCM grounds is on an engine block stud near the starter.
I checked all fuses and they are good. Ill have to check the ground your talking about to see if i may have hit a broke it. Where is it exactly?
Old Sep 30, 2022 | 06:09 PM
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Re: Vats system

Originally Posted by Injuneer
Any possibility you shorted something and blew a fuse? One of the PCM grounds is on an engine block stud near the starter.
and also I checked to see if I had spark when it turns over and I dont
Old Oct 3, 2022 | 12:10 PM
  #13  
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Re: Vats system

The Shoebox website has tons of info on the LT1:

http://shbox.com/1/g103.jpg

From your description, you have no fuel pump (controlled by the PCM, supplies 12 volts to the fuel pump relay signal side) and no spark (controlled by the PCM, supplies 12 volts to the Opti). No SES light (controlled by the PCM).

The risk in poking the jack handle at the starter was accidentally connecting 12 volts to the ground stud. Did you get an arc? Did that method cause the starter to function? May have damaged the ground stud, broken the wire, or back-fed the PCM and toasted part of it.

You can test the fuel pump by applying 12 volts to the fuel pump prime connector near the PCM:

http://shbox.com/1/fuel_pump_prime.jpg

The PCM has four 12 volt power connections. Two of them come from the ignition switch, through fuse #5 in the dash panel. Two of them are supplied direct from the battery, from a fusible link attached to the red plastic battery "+" box, then through fuse #8 in the under hood box. Did you check the fusible link?

http://shbox.com/1/1995_pcm3.jpg

Old Oct 3, 2022 | 01:49 PM
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Re: Vats system

Originally Posted by Injuneer
The Shoebox website has tons of info on the LT1:

http://shbox.com/1/g103.jpg

From your description, you have no fuel pump (controlled by the PCM, supplies 12 volts to the fuel pump relay signal side) and no spark (controlled by the PCM, supplies 12 volts to the Opti). No SES light (controlled by the PCM).

The risk in poking the jack handle at the starter was accidentally connecting 12 volts to the ground stud. Did you get an arc? Did that method cause the starter to function? May have damaged the ground stud, broken the wire, or back-fed the PCM and toasted part of it.

You can test the fuel pump by applying 12 volts to the fuel pump prime connector near the PCM:

http://shbox.com/1/fuel_pump_prime.jpg

The PCM has four 12 volt power connections. Two of them come from the ignition switch, through fuse #5 in the dash panel. Two of them are supplied direct from the battery, from a fusible link attached to the red plastic battery "+" box, then through fuse #8 in the under hood box. Did you check the fusible link?

http://shbox.com/1/1995_pcm3.jpg
no I never seen or heard a spark happen. But yes the starter did start turning over after that.
Old Oct 3, 2022 | 10:09 PM
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Re: Vats system

Originally Posted by shayhenderson88
no I never seen or heard a spark happen. But yes the starter did start turning over after that.
Do you mean that the starter ran while doing that or do you mean that the starter operated normal after that?



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