98 C1500 Starts but shuts off after 1 - 2 seconds

[Texcuda]

IIRC Passlock cuts power to the injectors on these trucks, not the pump. I'm betting this is a Passlock issue.

Yup it sounds like a Passlock issue to me too. It cuts power to the injectors, and the only way to get rid of it is to have it deleted in the PCM by a tuner.

Hmm, interesting. The forum posts I saw specifically state that Passlock shuts off the fuel pump, not the injectors, thus why I hot wired the fuel pump. The security light on the dash did not flash at all either, and it seems if the problem is Passlock related, the security light is supposed to flash at least a few times.

In that same vein, shouldn't I be able to keep it running on carb cleaner or gas poured directly into the throttle body, if the injectors are being shut off by the pcm?

Can you hear the fuel pump prime? Is the fuel relay engaging?

It has a brand new fuel pump and has 60 psi: key on, engine off; 52+ during initial crank and the 1 - 2 second run time.

You can bypass it, but the only way to eliminate it 100% is to disable it in the tune as @HotWheelsBurban mentioned. Everything else (including the resistor bypass in that South Main Auto YouTube vid) is just fooling the system into thinking it's operating properly. If another part of the system fails (like the module itself) the truck won't start again.

Disabling it in the tune will prevent the PCM from looking for a signal from the Passlock module permanently. Being a '98, the PCM is supported by HPTuners and EFILive so it shouldn't be too hard to find a tuner who can do it.

I may just spring for HPTuners as we've been talking about having the rear 02's tuned out and I can make some other changes as well.

Believe me, I tried everything with my '99 Burb when this happened. The truck would be fine, start every time for a week, and then you'd try to start it again and it wouldn't do anything. Just run for a few seconds and then quit. And keep doing that....
And of course when you really needed to get somewhere (like say, get to work on time) that's when it was most likely to act up.
So I googled the problem, and came up with this forum. And they told me the only sure thing was to get the PCM delete.....
So I did that, and no more problems.

Thanks for the info. Your truck's symptoms seem to match my son's exactly.

Gentleman, I truly appreciate the info and will report back with what I find. I'll start looking into HPTuners now as well.

 

[Texcuda]

Well Gents, deleting Passlock solved the problem! Thanks again for the advice!

 

[HotWheelsBurban]

Well Gents, deleting Passlock solved the problem! Thanks again for the advice!

Thank you, for coming back to tell the outcome!

 

[Dixieboy]

Believe me, I tried everything with my '99 Burb when this happened. The truck would be fine, start every time for a week, and then you'd try to start it again and it wouldn't do anything. Just run for a few seconds and then quit. And keep doing that....
And of course when you really needed to get somewhere (like say, get to work on time) that's when it was most likely to act up.
So I googled the problem, and came up with this forum. And they told me the only sure thing was to get the PCM delete.....
So I did that, and no more problems.

HotWheels, I seem to have similar issue with my Tahoe. I dont have any lights or codes. My security light is not on. How/who did you delete passlock, A local person or shop? I don't how to do this or how it works. Thanks

 

[HotWheelsBurban]

HotWheels, I seem to have similar issue with my Tahoe. I dont have any lights or codes. My security light is not on. How/who did you delete passlock, A local person or shop? I don't how to do this or how it works. Thanks

I talked to the guys in a local shop, that I knew had some experience with GM trucks from the '90s and early 2000s, and they recommended another shop in the general area, that did a lot of work on LS platform vehicles and engines. We took the Burb to them, explained what it was doing, and asked if they could help. In the meantime I had been on this forum, and had learned what could be done with a tuning program.
Long story little shorter, they had the Burb for about an hour, and electronically deleted the Passlock program from the PCM. It cost me $250(a lot of that was the software license fee; the tuning programs are licensed to individual VINs). But the few times it hasn't wanted to start, I know it's something else. That $250 got it behaving properly!
So if you know someone who does "tuning" with LS powered vehicles, they should be able to do something for you(but it probably won't be cheap).