Theft-deterrent switch

ID Status Date Year Make Model Transmission Type A/C Controls Public/Private
#16751 Closed 1999 Chevy Silverado public

For a theft deterrent switch, I’m thinking of using 2-part butt connectors to rewire the load-side of the UBEC fog lamp relay to be in series with the load side of the UBEC fuel pump relay, then repin the cargo/fog harness connector under the dash so that the cargo light switch operates the coil of the fog relay.

Do you know if this would mess up anything? Any comments?

Hi, I’m logged in but am unable to see my previous replies in this thread/ticket. I suspect that is because I clicked ‘Make Private’ on the individual replies. Can you make them visible again? Sorry for the hassle.

FWIW, I just read in the Owners Manual on page 2-53 that if fog lights will go off whenever high-beams come on. I guess that is caused by the fog relay solenoid being controlled by the BCM.


I would tend to stay away from wanting to interact with any switch or relay that is directly wired to the BCM or PCM. The BCM in particular since they are prone to failure and locked to a VIN.

Are you sure that your truck does not have a factory anti theft system? There would be a light that comes on with cycling the key on that states “security”, “theft” or a picture of a lock.

Yeah, almost positive that my base model truck does not have a factory anti theft system.


Okay, If it were me and wanted a discreet anti theft switch I would buy and install a factory style fog/cargo light switch. Then I would wire in the previously unused fog light portion to activate the aftermarket installed relay under the dash. The relay should only draw  between .5 and 1 amp and only when the ignition switch is in the crank position. Turn the fog light switch off and the starter will not work.

Besides the switch and relay you should only need a couple of wires and terminals to install in the correct socket locations (positions G & F) in the factory harness. There are less expensive versions but sometimes the graphics are a little off compared to OEM.

Link to recommended part on Amazon

I believe the truck could be push started, so I was aiming for a switch to cut the power to the fuel pump, and possibly a second switch to disable the ignition control module.


If it has a manual transmission it could be push started without a lot of trouble.

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