I have a 2012 GX 460 and it will not start. The power comes on, AC, lights, everything, but it gives the error to depress the brake pedal. After replacing the battery on my key fob and it still not starting, I checked the engine fuse box and found the STOP fuse blown. I pulled it and replaced it with another 10A fuse. I then pressed on the brake pedal and I heard it pop again and checked it and it was blown. I pulled it and replaced it again.

I bought and replaced the brake light switch, and it then started and ran fine for a few hours. I drove it around and stuff. Then came home and parked. A few hours later went out to start the car to leave and it did not start and the fuse was blown again.

I am not sure what it blowing the fuse. Kind of interesting that it happens when pressing on the brake pedal to start the car and the car does not start. The rear brake lights do not light when I press on the brake with the fuse blown also. I pulled them out, both sides, and checked the bulbs and they look fine. The both worked before I started having this problem also.

Any ideas where to go now? Thanks!

 

first determine which path pulls the over current. looks like there are a couple easy places. also could see if it blows without the relay. whats below should match 2012.

 

***UPDATE***
I purchased a new Stop Relay and pulled the old one and placed the new one in and I have not had the Stop fuse blow again. I replaced the new stop (brake) light switch with the old one and it is still working perfectly, no issues.

If you are having the issue of your Stop fuse popping each time you step on the brake to start the car, then check your Stop Relay.

Hope this can help someone out there. . . .

 

That's great news!
Thank you for the update too.

 

***3 month update***
The stop fuse is blowing again. While driving, I am getting a PCS error. When I turn the car off, it will not start again and the Stop fuse is blon.

I have removed the power to the trailer connection in the rer, thinking that may be the issue, but it did it again today.

Anyone else have this issue with the PCS error and Stop fuse?

 

I have been looking over the factory wiring diagrams and the service manual this is what I found, which is very interesting

Your PCS error is almost certainly a secondary symptom, not the root cause of the failure. Here is a breakdown of what's actually happening and how to permanently track it down.The Pre-Collision System relies entirely on the braking system to function. Your stop light switch transmits an STP signal to the ECM and other control modules so they can monitor whether the brakes are working. The exact moment your 10A STOP fuse blows, the system loses that vital pedal status signal. The computer immediately detects the malfunction, disables the PCS for safety, and throws the error on your dash. It's happening because the fuse blew when you pressed the brakes, not because your expensive Brake Actuator is failing.

The standard STOP LP Relay is located inside the Engine Room Relay Block under the hood. When you pulled the old relay out and pushed the new one in 3 months ago, you had to apply physical pressure to the relay box and the wiring harnesses underneath it. It is highly probable that you shifted the harness just enough to pull a chafed wire away from a metal ground point. After 3 months of engine vibration and driving, that chafed wire finally rubbed back against the chassis, causing the direct short to ground to return.

You mentioned that you removed the power to the rear trailer connection. If you only disconnected the main 12V power feed wire going to an aftermarket trailer converter box, the signal wires are still physically tapped into your GX's green brake light circuit. If the converter box has an internal short to ground, or if the T-harness adapters are pinched behind the bumper, stepping on the brake pedal will still send 12V straight into that short and blow the fuse. You have to physically unplug the trailer T-harness adapters from the left and right taillights to completely isolate the trailer wiring from the vehicle.

Don't keep blindly throwing parts or fuses at it. The factory service manual outlines a specific method for finding short circuits like this without wasting a whole box of fuses:

Remove the blown 10A STOP fuse and connect a 12V automotive test light across the two empty terminals of the fuse slot.

Establish the condition that causes the short by depressing and holding the brake pedal (just wedge something against it). Because you have an active short to ground, the test light will illuminate brightly.

While the light is on, start isolating the circuit by disconnecting connectors. First, completely unplug those trailer wiring T-harnesses from the taillights.

If the light stays on, open the hood and firmly wiggle the wiring harnesses directly underneath the Engine Room Relay Block where you replaced the relay 3 months ago. Try to find the exact location of the short by lightly shaking the problem wires along the body.

The exact moment the test light goes out, you have successfully isolated the shorted component or the section of chafed wire.

Hope this helps keep us posted if anything changes!