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99 Starts then immediately dies

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My 99 Yukon with Vortec 5.7L suddenly won't run. It cranks over fine, starts in about 1 second (normal), but then dies 2-3 seconds later. Giving it a little bit of throttle while starting doesn't make any difference.


I was out of town when it happened, so I had to have it towed to the nearest shop. I suspect the fuel pump, but my search of the forum didn't turn up any other posts with this problem.


Is this common? If not the fuel pump, any ideas what could be causing this start, but quickly dying, problem to suddenly appear? I also considered the fuel filter, but it seems unlikely it would behave this way suddenly. It's been a while, but the last time I checked the fuel pressure, it was right around 60 PSI.

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The next day, when the shop tried, it started and ran just fine! It's been starting and running fine ever since. So, my suspicions about the fuel pump were wrong!

The found a stored P1626 code, which means there was a communication problem between the Theft Deterrent Module and the PCM. When it doesn't receive the right password, it disables the fuel pump. When the key is turned to on, the fuel pump comes on to prime the system, so it will run for a couple of seconds, but then the PCM will turn the pump off if all is not well immediately after start. It may have just been a glitch, but now it makes me wonder.


The shop tech said there could be 3-4 things that could cause the code to be set. Anyone have experience with this kind of problem and fixing it?

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  • 2 weeks later...

Well, it's been over 2 weeks now and it's been starting and running fine, so I guess it was just a glitch in the Theft Deterrent / Security system.


I'm grateful it didn't cost tons of money to fix, but don't know what else (besides a flaky connection) might have caused it.


The biggest question is: when will it happen again?

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  • 10 months later...

And... the answer to my big question is: in about a year!


I have had no hint of any kind of problem during the past year, but today it wouldn't run again. This time I was in a campground about 20 miles from cell phone coverage.


The shorter version of a MUCH longer story is that it started about 3 hours later. In the meantime, disconnecting the battery and trying my backup key made no difference. It's like the brains were temporarily scrambled in one of the computers and then, for some inexplicable reason, at some point, things get straightened out again.H


Have you had to fix this problem?

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I had the ignition key lock cylinder replaced about 10 years ago to try to fix a similar problem. It may be time to try that again. I read somewhere that the lock cylinder can wear and tiny pieces of metal can cause problems with it working right as far as reading the key or sending the signal properly. Apparently, the BCM (body control module) is where the theft-deterrent system is located. It *could* be that, as well.

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  • 2 weeks later...

I just got it back from the shop today. After calling around to a few different places, I decided to take it to the dealership because they had the most experience with this kind of problem. As expected, they were not able to reproduce the problem in the shop. They said this was not the typical failure of the theft deterrent system. They found the same P1626 code stored, in history, as last year. The tech suspects the theft deterrent module (apparently located under the dash) is not powering up when the problem occurs. They recommended a new module, but the part is discontinued. I can find a used part, of course, but it may not be as simple as just swapping out the module (that is, the system may have to re-learn the passcode).


They said they can modify the Powertrain control module (PCM) so that it will allow the engine to run if the passcode is missing (involves about one hour labor). Assuming that approach is successful, it may be the way to go if it will prevent the theft deterrent system from disabling the fuel pump AND it will work if the problem lies with the lock cylinder, Passlock module, theft deterrent module or the wiring.


Anyone have thoughts or experience on modifying/reprogramming the BCM to ignore a missing passcode? Anyone replace the theft deterrent module in the middle of the dash, underneath the radio?


I'm not especially concerned about someone stealing the truck with a screwdriver or the wrong key because I have an aftermarket starter interrupt device (it was in the truck when I bought it).

Edited by lunytnz
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I would bypass the passlock system first. There are many YouTube videos and articles how to do this for roughly 40 cents. I had the same issue. If it doesn't work your out a buck and some time. Plus you bypassed most potential issues in the steering column.


Good luck.


Thanks for the idea! Unfortunately, I didn't see it until after I got back from having the PCM reprogrammed. In my case, they said they believed the problem was that the PCM wasn't receiving any security message at all. Maybe your bypass approach would work in that situation... I'm not sure. Like you, I believe (based on what they told me) the change they made to the PCM resolves this problem. I'll let you know in a year or so :-)


Where did you wire in the 2200 ohm resistor?

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