Why do my brake lights come on when I turn the ignition on?

The brake light switch is where Id look first.

I can check there first. I looked for 2 years for a transmission for the truck cause it was given to me by my brother then had to find a motor for it. So got the motor in and trying to get it back on the road and running. Thanks.

If the brake light does not extinguishes, the problem is electrical. Check and see if the brake light cables are chaffing

check your bulb? might be put in wrong? when switch goes bad normaly the thrid brake light only works. yes also check switch, sometimes they get kicked, but its either bad (switch) or bulbs are in wrong? also do your test with the light in the on position

Did this ever get resolved? I'm having the same issue In my 98 gmc. Tried a switch, bulbs. Circuit boards in tail lights, multifunction switch, replaced all the ground wires and checked harness wires

Ok I was having the same issue, found the engine lamp connected to under the hood on the passenger side had a burnt ground wire. Cut and spliced in a new ground wire connected it to the mounting screw for the engine compartment light and that fixed it.

Did you ever figure out what was wrong? My 98 just started doing this after sitting up for 3 months while I was out of town on a job