Passlock relearn procedure not working

[etap_franklin]

Good afternoon y'all. I just replaced my ignition switch in my 2000 OBS K3500 Pickup. I've tried twice now to do the 3 round relearn.

Crank and let it shut itself off immediately.
Leave key in the run position for 10 minutes.
Turn key off for 10 seconds.
Crank truck again.
Complete a total of 3 times.

I've done this twice already with no success.

One thing that sticks out is that everyone says that after 10 minutes, the solid security light should turn off, buy mine doesn't turn off even if I wait for 12 or 13 minutes.

Any ideas?

 

[etap_franklin]

May have figured it out....I'll update.

 

[etap_franklin]

May have figured it out....I'll update.

I was wrong about figuring it out. Any help would be appreciated.

 

[etap_franklin]

I turn the key on, security light stays on for 5 seconds or so which I believe is just the normal bulb check.

I crank the truck and it promptly kills itself.

The security light flashes for a few seconds and then turns off.

Relearn procedure tried multiple times with no success.

I read that the security light flashing a few times means the PCM is in short tamper mode, but I can't find what to do about it.

 

[etap_franklin]

I realize I'm talking to myself but eventually someone else may see this and at least I'll have my thoughts down. If my security light just runs through the bulb check when I turn the key on, that would indicated no Passlock problem, but the crank and then stall would indicate a Passlock problem.

 

[PeteyG708]

Mine will show the Security light for 5 seconds on the bulb check, and then go off if I switch it only to Run. If I am in Run and then go to start it, it does the same 5 second bulb check again.

However, if it is flashing, that could indicate an issue. I wonder about the passlock on these trucks though... I had to remove my ignition cylinder and have it redone (cleaned and new keys cut from the cylinder itself) and even when I put it back in, it worked flawlessly. I cannot remember if I “test installed” the new cylinder before attempting to re-key it. Additionally, I am using a flat key (not the original GM plastic clad key) as that is what he used to cut it, and it has no issues with the passlock. I might be mistaken as to how it works on the GMT400s as opposed to other GM products of this era.

 

[etap_franklin]

The ignition harness I put it must have been faulty. It wouldn't come out of short tamper mode. I think the passlock wiring may have been defective because I picked up a new one, installed it, and everything is just fine.