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Old 05-31-2015, 07:11pm   #21
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Well here are the results:

When grounding the yellow/black wire, it fires right up. (of course it doesn't run

There is a code B2723 Passkey Detection circuit and I may (hopefully) have some more insight:

For the last few months, (Vette is not DD) EVERY time I tried to start it the first attempt would result in the car cranking but not starting. Like clockwork, the 2nd attempt immediately after the first no problems. I just didnt think anything of it. The ignition lock cylinder looks "worn" (See pic) and there was once where it seemed as though the key was not going in smoothly, hence I stopped and reinserted it.

I am wondering if this may be the issue.

Thoughts??

Thanks again,

Barry

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Originally Posted by Y2Kvert4me View Post

What I would do next is tap into that yellow/black wire coming out of the TDR, and connect a jumper wire from it to a verified good ground point.. Leave everything connected to the TDR as normal.

-If it does crank for this test, then it seems the BCM is inhibiting starting by not switching that yel/blk wire to ground during starting. You've already indicated this may be the case, this just proves it.

If it is the latter, it's possible the engine won't fire and run due to other protection features of the BCM, but you've at least narrowed it down to this. Though I'd think if the BCM were inhibiting start, there'd be other indicators...Security light or BCM codes, not sure.
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Old 05-31-2015, 08:19pm   #22
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Yes, that helps a lot, and that is most likely the problem.

It appears the ignition lock cylinder (GM part#12458190) contains the key pellet sensor, and electrical pigtail which connects to the BCM. It's about a $100 part and appears to be readily available.

I've never dug into this before, but since you seem to be good with electrical stuff, I believe you can bypass this sensor by unplugging that lock cyl connector (the one that contains just 2 white wires), and connecting a resistor of the same ohm value as your key pellet into the connector that leads to the BCM (leaving the switch pigtail disconnected). Might be worth trying before you drop $100+ on a new cylinder....If you have a Radio Shack or source for electronic resistors near you that is...


To measure your key pellet, just set your meter to ohms, and probe each side of the pellet in the key. There are 15 possible resistance values:

402 (ohms)
523
681
887
1.13k
1.47k
1.87k
2.37k
3.01k
3.74k
4.75k
6.04k
7.50k
9.53k
11.80k

You may need a combination of resistors in series to add up to the correct value needed to match your key. Solder the resistor(s) to some wires to create a jumper loop that plugs into the connector leading back to the BCM.
That should bypass it, and the car should then start and run. If it does, then you'll need to replace the ign lock cylinder to correctly fix it.

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Old 06-01-2015, 12:43am   #23
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Thank you for all the info. I figured since the key had a resistor in it I could "trick it" But I am a firm believer in doing it right. So I will replace the lock cyl. regardless however I will test the theory with a resistor of the proper ohm rating.

Update to follow




Quote:
Originally Posted by Y2Kvert4me View Post
Yes, that helps a lot, and that is most likely the problem.

It appears the ignition lock cylinder (GM part#12458190) contains the key pellet sensor, and electrical pigtail which connects to the BCM. It's about a $100 part and appears to be readily available.

I've never dug into this before, but since you seem to be good with electrical stuff, I believe you can bypass this sensor by unplugging that lock cyl connector (the one that contains just 2 white wires), and connecting a resistor of the same ohm value as your key pellet into the connector that leads to the BCM (leaving the switch pigtail disconnected). Might be worth trying before you drop $100+ on a new cylinder....If you have a Radio Shack or source for electronic resistors near you that is...


To measure your key pellet, just set your meter to ohms, and probe each side of the pellet in the key. There are 15 possible resistance values:

402 (ohms)
523
681
887
1.13k
1.47k
1.87k
2.37k
3.01k
3.74k
4.75k
6.04k
7.50k
9.53k
11.80k

You may need a combination of resistors in series to add up to the correct value needed to match your key. Solder the resistor(s) to some wires to create a jumper loop that plugs into the connector leading back to the BCM.
That should bypass it, and the car should then start and run. If it does, then you'll need to replace the ign lock cylinder to correctly fix it.

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Old 06-01-2015, 08:48am   #24
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Quote:
Originally Posted by Barry B View Post
Thank you for all the info. I figured since the key had a resistor in it I could "trick it" But I am a firm believer in doing it right. So I will replace the lock cyl. regardless however I will test the theory with a resistor of the proper ohm rating.

Update to follow

Barry,

I replaced my lock cylinder and it is not a difficult job. Especially since you obviously know your way around. I didn't have to worry about any resistor values etc. because I bought a blank cylinder and transferred everything over. I actually changed my tumblers over so I didn't need to have a separate key. A locksmith can do this if you are not comfortable with it, but it was pretty easy. I will dig around and see if I can locate the documentation on it. I took pics etc. and started to do a full write up, but never finished it.

Jeff
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Old 06-01-2015, 10:47am   #25
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Quote:
Originally Posted by aerovette View Post
I didn't have to worry about any resistor values etc. because I bought a blank cylinder and transferred everything over.
The resistors create a bypass of the cylinder sensor. They mimic the key pellet resistance which is how the BCM verifies the correct key is being used and allows the car to start and run.

He doesn't have to do that if he replaces the cylinder. I posted that as a cheap diagnostic option, something he could do to confirm the cylinder is indeed the culprit...It most likely is, but nothing is an absolute until the problem has been solved. The resistor trick might cost a couple bucks at most...Sure beats replacing a $100+ part only to potentially discover that isn't the problem.

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Old 06-01-2015, 12:14pm   #26
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Thanks Jeff. Any information will help. It did look pretty simple, at least at my skill level. I most likely will not change the tumblers myself, I have a good locksmith we have used before. I would definitely like to see what you do have, I may try it myself

Thanks for the input and tips!

Barry

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Barry,

I replaced my lock cylinder and it is not a difficult job. Especially since you obviously know your way around. I didn't have to worry about any resistor values etc. because I bought a blank cylinder and transferred everything over. I actually changed my tumblers over so I didn't need to have a separate key. A locksmith can do this if you are not comfortable with it, but it was pretty easy. I will dig around and see if I can locate the documentation on it. I took pics etc. and started to do a full write up, but never finished it.

Jeff
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Old 06-01-2015, 12:16pm   #27
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Correct, I am just using the resistor for troubleshooting. IMHO it wold be not smart to leave the Vette vulnerable like that.
(Plus I would never live it down) LOL

Barry


Quote:
Originally Posted by Y2Kvert4me View Post
The resistors create a bypass of the cylinder sensor. They mimic the key pellet resistance which is how the BCM verifies the correct key is being used and allows the car to start and run.

He doesn't have to do that if he replaces the cylinder. I posted that as a cheap diagnostic option, something he could do to confirm the cylinder is indeed the culprit...It most likely is, but nothing is an absolute until the problem has been solved. The resistor trick might cost a couple bucks at most...Sure beats replacing a $100+ part only to potentially discover that isn't the problem.

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Old 06-02-2015, 02:11pm   #28
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This may be a silly question, but I don't want to blow up anything.
Does the wattage matter?

Thanks

Barry
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Old 06-02-2015, 02:31pm   #29
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1/4 or 1/2 watt are known to work fine, and you'd probably not want to work with anything smaller than that anyways (1/8w are tiny).

Given the choice, I'd use 1/2w.
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Old 06-03-2015, 10:10pm   #30
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I finally was able to get the time to make the Vats bypass,(Solder the proper number of resistors inline, heat shrink tube them, and plug them in) and that was the problem, she fired right up ran fine. I drove around and ran some errands taking the loop I made in with me at each stop So I will order a new lock cylinder and install it and pay to have it coded if needed.

Thank you very much to everyone for all the help!
And if anyone needs assistance in creating one of these bypasses, I am happy to help.

Barry
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Old 06-03-2015, 11:13pm   #31
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My local locksmith wanted $135.00 for the job. That was enough for me to decide to do it myself. The replacement cylinder was purchased on Amazon for about $60.00 if I recall. I may have that wrong. I've slept since then.
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Old 06-04-2015, 06:13pm   #32
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That is about right and what I have found after a few phone calls and research. I have one on the way

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My local locksmith wanted $135.00 for the job. That was enough for me to decide to do it myself. The replacement cylinder was purchased on Amazon for about $60.00 if I recall. I may have that wrong. I've slept since then.
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