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

No crank Vats?

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Old Feb 15, 2020 | 03:53 PM
  #1  
Ryan Harrington's Avatar
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No crank Vats?

So I have a 1994 z28 that I lost my only key for I replaced the key tumbler the car would turn over but not crank the security light would stay on I then went through the 15 resistors I found out resistor #3 the security light will cut off but still no crank. I then hot wired the ignition and got the car to turn over the car is getting fuel and air but no spark I then plugged the ignition connector back in but now it will not turn over a small black box labeled P.E.D makes a funny noise under the dash and also the box where the brake lines come from. The car ran fine before I lost the key.
Old Feb 15, 2020 | 04:13 PM
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DrewHMS97SS's Avatar
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Re: No crank Vats?

Did you give time between each try. If I recall correctly, after the second failed resistance, even with the right one there is a 5 minute lockout.
Old Feb 15, 2020 | 04:58 PM
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Re: No crank Vats?

See if this helps:

4th Gen LT1 F-Body Tech-PassKey/VATS

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

You need to clarify the use of the terms “turn over” and “crank” so we can understand what happens when you turn the key to start. Not everyone uses thos terms the same way. The PASS-Key system has two stages.

When the TDM recognizes the key, it allows 12 volt power to reach the control side of the starter relay (TDR). If the starter engages and cranks the engine, the key/resistor circuit is fine. Then the TDM sends a 50Hz signal to the PCM, allowing the PCM to activate the injectors. When you say “the car is getting fuel”. do you mean the pump has primed and the system has pressure? Or have you actually verified the injectors are pulsing?

Last edited by Injuneer; Feb 15, 2020 at 06:27 PM.
Old Feb 15, 2020 | 06:09 PM
  #4  
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Re: No crank Vats?

And, “New Member Intro....” isn’t the best place for tech issues. I'll move this to the correct forum.
Old Feb 20, 2020 | 04:27 AM
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Ryan Harrington's Avatar
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Re: No crank Vats?

Originally Posted by Injuneer
See if this helps:

4th Gen LT1 F-Body Tech-PassKey/VATS

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

You need to clarify the use of the terms “turn over” and “crank” so we can understand what happens when you turn the key to start. Not everyone uses thos terms the same way. The PASS-Key system has two stages.

When the TDM recognizes the key, it allows 12 volt power to reach the control side of the starter relay (TDR). If the starter engages and cranks the engine, the key/resistor circuit is fine. Then the TDM sends a 50Hz signal to the PCM, allowing the PCM to activate the injectors. When you say “the car is getting fuel”. do you mean the pump has primed and the system has pressure? Or have you actually verified the injectors are pulsing?
i believe the fuel pump is priming I’m thinking the TDM is not sending any signal to the starter or the injectors is there a easy way to fix this I don’t have a lot of experience wiring is it possible to get a new TDM I am 100 percent certain I have the right resistor for the bypass it’s the only one that makes the security light turn off
Old Feb 20, 2020 | 07:54 AM
  #6  
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Re: No crank Vats?

From Freds first post, read all the way through the writeup. Yes the TDM can be replaced, but be 100% sure that is the issue. For one, getting the module out, at least for me was a pain in the neck. If you come to this point, call Hawks Motorsports, they may be able to help with a used replacement.




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