99 k1500 suburban passlock issues

[99gmck1500]

Alrighty I've been fighting an issue with my 99 k1500 gmc suburban with the anti theft system. Long story on how I got this suburban was back in 2020 I bought it for 500 bucks. Had to put in injectors an a starter an still had an issue with it starting didn't realize the theft system was tripped on. Watched a video on YouTube an got it to work. Fast foward to 2022 I've been having intermittent issues with it. Security light would stay on an won't start then like 6 mins later it would turn off an bam starts up an that for a week. Well now it's gotten weird it would stay on an start up then shuts off. At times it would take 1hr or so to get the suburban running. Now it won't even start at all now like starts up then stalls. I've done the reset procedure 6 times. Ive disconnected the battery for an hr. Now herese a weird part. If i disconnect the anti theft module the security light would go off an still wouldnt start .I've had it towed to where I work at due for the fact I'm a mechanic an have all the scan tool. But won't be there till Tuesday after labor day. Any suggestions on what is going on with the whole truck. I really don't want to sell it but I've been tempting to sell it when I get it fixed. Any help be awesome. Thank you

 

[HotWheelsBurban]

I had a similar issue with my 99 C1500 Burb in 2019. That's what eventually led me to this forum! I tried all the "relearn/reset" procedures, and usually they worked a couple of times, then I'd have to try another one. It was suggested to me, to find someone with tuning software, and get them to electronically delete Passlock from the ECM. So I did a little research, and found a shop in my area ( just outside of Houston, Texas) that mainly works on and tunes LS powered vehicles. Went to them with the Burb and asked them what they could do and how much they would charge. $250 and an hour later, they said it was fixed. They'd started it multiple times and it always started. 3 years later, still does.
The Passlock module has a bunch of printed circuits in it, that come undone after 20+ years of bouncing around in these trucks. I've heard of people resoldering the connections and "remanufacturing" the boxes( like the wiper motor boards) but never tried one. I also never tried the resistor bypass, because I didn't want to hack into the column, and I didn't want the truck to be easier to steal. I've heard that the resistor eventually gets to where it no longer works, because its resistance changes.
Hope this helps....

 

[stutaeng]

Do you know anyone with HP Tuners? Or have any local tuners in your area?

There's also tuners you can mail your ECU so they can delete the Passlock.

 

[99gmck1500]

Do you know anyone with HP Tuners? Or have any local tuners in your area?

There's also tuners you can mail your ECU so they can delete the Passlock.

I'm located in upstate south carolina. I've got to see who's around an can do it.

 

[618 Syndicate]

You can pull the PCM and send it off if you can't find anyone local.

 

[99gmck1500]

So little update on the suburban. Had a code for the passlock. B2948 code. I cleared it an started up fine. Let it sit for couple days an still starts. Fast foward to today its doing the same thing. I'm just thinking of find an old scan tool that can go through the system an clear the codes an keep in the back just in case it starts acting up

 

[618 Syndicate]

So little update on the suburban. Had a code for the passlock. B2948 code. I cleared it an started up fine. Let it sit for couple days an still starts. Fast foward to today its doing the same thing. I'm just thinking of find an old scan tool that can go through the system an clear the codes an keep in the back just in case it starts acting up

It's gonna act up again, and probably at the worst possible time.

 

[HotWheelsBurban]

It's gonna act up again, and probably at the worst possible time.

Yes I agree, been there done that! My Burb cost me a buncha money on rental cars, summer of 2019. The relearn procedures only works a couple of times, then you're back to square 1. Tuning it out(electronically deleting it) is all that works.

 

[east302]

So little update on the suburban. Had a code for the passlock. B2948 code. I cleared it an started up fine. Let it sit for couple days an still starts. Fast foward to today its doing the same thing. I'm just thinking of find an old scan tool that can go through the system an clear the codes an keep in the back just in case it starts acting up

Here’s the GM diagnostic for that code in a 1998. Possibly the same for the 99, but might be worth going through.

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[Darkimag22]

Had a very similar issue with my 98 last winter. Ended up buying the HP Tuners OBDII device and turned the security off myself. At the same time I turned off the downstream O2 sensors as I removed the cats. It's super easy to do yourself if that's the route you are thinking of taking.