Likewise, the transmission interlock won't allow you to shift out of PARK until it receives a signal from the <b>brake</b> <b>light</b> <b>switch</b>. A bad brake light switch, for example, can trigger the ABS and traction control lights, but it can also prevent engine start or even transmission shifting. The brake light switch is usually attached to a small bracket that holds the switch, activated when the pedal is depressed, in position. If fluid level is acceptable, move on to Step 5.