Q: What Is the Function of the Brake Transmission Shift Interlock (BTSI) System and Neutral Safety Switch and How Do You Diagnose or Replace It on Toyota Highlander?
A: In the Highlander, the Brake Transmission Shift Interlock (BTSI) system operates through two solenoid-controlled components: one located near the ignition key cylinder, and another on the shift lever assembly under the center console connected to a Shift Lock Module that requires signals from the brake pedal switch and the transaxle range sensor to work. The system won't let you take your car out of PARK unless you press down on the brake pedal first. Check these three things: make sure you can't pull out the ignition key when the car isn't in PARK, that the key can spin from OFF to LOCK position only when you're in PARK, and that you can't move the gear out of PARK unless you press the brake pedal when the key is OFF, RUN, or START. When the system doesn't work correctly, fix it by starting with turning the vehicle's negative battery disconnect cable off. To replace the key lock solenoid, lift off the steering column trim, free the electrical connection, turn the solenoid off the key lock cylinder, working backward for reassembly. To remove the shift lock module, remove the shift lever assembly, disconnect the console lamp, part the shift overdrive harness wire ends, pull off the shift lever button, and unscrew the module from the assembly, repeating these steps in reverse to install everything back correctly. When you shift into Park or Neutral, this sensor stops your engine from turning on, but you have to set it right if it lets you start the engine in the wrong gear. If the BTSI (Button Shift Interlock) stops working, you can use a manual override by pressing a button located near the shift lever while the ignition is set to LOCK position. Note: newer models have put a protective cap on this manual button.