1998 K2500 Passlock/VATS Question

That’s how i got my truck for so cheap. Guy thought it was a bad fuel pump. I bought and right in the driveway did the reset and drove away. Guy was so pissed lol

I know this is of no help but I had the same issue with my 98 K1500. My mechanic took my truck and got rid of the factory security and all was well after that. What he did to fix that, I couldn’t tell you.


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I have a 91 with the guts of a 98 swapped over. Mine would not stay running with the module under the dash unplugged. I found this out when I forgot to plug it back in after removing and reinstalling the dash. I fairly quickly figured out what I missed and it ran fine once I plugged it in again. A few months later I had the truck dyno tuned by a local shop and had him to disable the VATS system. I believe they used HP Tuners. He cautioned me that the light would still come on briefly but the system really is disabled. It does not stay on after startup. I have the 98 blackbox PCM.

I never had any issue with the VATS, but figured having him tune it out would help prevent any problems. I have wondered if it'll run without the VATS module now that it's disabled in the PCM, but haven't tried it.

s98gmc said:

I have wondered if it'll run without the VATS module now that it's disabled in the PCM, but haven't tried it.

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That would be an interesting experiment. Too bad that the module looks really hard to get to without disassembling the dash.

Ok, so I went out and cut the yellow Passlock wire so I could trigger the security light and then work backwards from there to know that what I was doing was working.

Cutting the yellow wire didn't trigger the security light to stay on.

What??

https://streamable.com/qk7et

df2x4 said:

That would be an interesting experiment. Too bad that the module looks really hard to get to without disassembling the dash.

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You're right. I did have to pull apart some of the dash and I don't think it's worth the time (plus I don't remember how much had to come out). I did have some time this afternoon so borrowed your suggestion and removed the bulb. The only reminder my truck still had VATS was the security light on startup. Now that's gone too.

I think the resounding theme of this thread so far is that if you disable PassLock in the PCM, you shouldn't have to worry at all about it preventing you from starting the vehicle. Regardless of the security light or anything else, I haven't seen anyone report any actual functional issues after disabling PassLock in the PCM.

df2x4 said:

I think the resounding theme of this thread so far is that if you disable PassLock in the PCM, you shouldn't have to worry at all about it preventing you from starting the vehicle. Regardless of the security light or anything else, I haven't seen anyone report any actual functional issues after disabling PassLock in the PCM.

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Gonna have to say I agree.

Its weird because I went into this hearing everyone say that if you disable Passlock/VATS, the security light will stay on solid, and if you want to fix the security light, you'll have to fix the VATS system.

Given the wiring diagram and how the VATS box seems to directly control the security light, etc, I thought it had to be that way.

The only thing I can think of is that circuit 1807 gives the PCM bidirectional control of the VATS box and it /tells/ the VATS box to ignore everything? I figured the PCM VATS delete just told the PCM to stop looking for the injector kill signal but thats all I've got... and I don't feel like going further for now so my idea to make a guide to rip out the box is bunk, sorry, no way I'm turning VATS back on to have a means to troubleshoot doing so.

I'm sorry. I had to.

I had passlock issues with my 98 and replaced the module under the dash to fix it. Afterwards I got a blackbear tune and had them disable it and it's been smooth sailing ever since.