Security System Triggered Fuel Shut Off 1999 GMC Sonoma

I brought my neice's 1999 GMC Sonoma to my mechanic to change the idler arm and trans pan gasket. On the side of the trans there was a O2 sensor, aside from touching that, no electrical work was done. Somehow the security system triggered the fuel shut off. She never had a FOB with the truck. Its an early 1999 model. I ordered a slim E4 torx from GM to try to remove the steering housing cover so I can access the ignition switch to make sure the plug is in there tight as some online blog stuff says that the plug comes loose. In case that isn't the problem does anyone know anything about the security system shutting off the fuel and what else I can try to do?

I am assuming you have a security light flashing.

The standard security reset procedure for GM is:

1. Insert ignition key and turn to the “ON” position. Do not attempt to start the engine. Leave
the key in the “ON” position for approximately 10 minutes. The security light will be steady
on or flashing for the 10-minute period. Do not proceed to Step 2 until the security light
turns off or stops flashing.
2. Turn the ignition switch to the “OFF” position for 30 seconds.
3. Turn the ignition switch to the “ON” position as in Step 1 for 10 minutes.
4. Turn the ignition switch to the “OFF” position for 30 seconds.
5. Turn the ignition switch to the “ON” position as in Step 1 for 10 minutes for a third time.
6. Turn the ignition switch to the “OFF” position for 30 seconds for a third time.
7. Turn the ignition switch to the “ON” position for 30 seconds.
8. Turn the ignition switch to the “OFF” position.
9. Attempt to start the engine.
If the engine starts and runs, the relearn is complete.

The entire process takes a little more than 1/2 hour, so you may want to use a battery maintainer/charger.

Are you sure that's what the issue is?

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