2000 Silverado 1500 – Security Light / No-Run After Stalk Replacement
• Truck always ran fine, just never had cruise.
• Installed new cruise stalk/module → truck starts, then immediately dies (SEC light on). Same with old stalk reinstalled.

• Installed new spark plugs and wires (already had them) → no change.

• Tried 30-minute relearn → SEC light never went off, even after 20+ min.

• Fuses good (under hood):
• IGN 0 – 50A
• IGN 1 – 40A
• ECM B – 20A
• ECM 1 – 20A

• Suspected weak battery from leaving key ON → hooked up Harbor Freight charger, holds 12.6–12.7 V.

• Tried resistor bypass (2.2kΩ across yellow + black/orange at ignition lock connector) → relearn still failed.
• No voltage on yellow or white wires at ignition connector under column.
• Pulled BCM, checked blue connector:
• Yellow to black/orange: 0.20–0.30 V KOEO, rises to ~2 V while cranking.
• Same results at connector side and harness side after cutting wires.
• Security light stays solid, even overnight.
• End of the road: fuses fine, battery stable, SEC light never leaves, yellow wire never shows proper 5 V ref or mid-range return. Feels like BCM circuit or feed/ground issue — but I’m tapped out.

So it was fine and you did what exactly after which this happened. What electrical systems did you work on EXACTLY?

On many of the modules (not all but several) you have to program your VIN into the module or it fails the security check. Based upon what your describing, it appears the VIN will need to be entered into that module. I drive 2000-2005 LeSabre'* and I have been able to go into the serial EEProm on the modules which need the VIN, find the VIN in the EEProm image and enter it. The attached PDF shows how I did this for the radio. All the other relevant modules have been basically the same process. If your not comfortable with this, my understanding is you can take it to a GM dealer and they can connect and enter the VIN through the Class II bus. I've never used a dealership for this but my understanding is they charge something in the neighborhood of $150. I would conform with them first that this module does need tour VIN entered.

I'm guessing broken wire somewhere near where you were working.