Hey, I'm getting a code P0571 on my '05 Lexus ls430. The electricians here have 0 clue as to how to fix it. My radar cruise control works but as soon as it detects a car ahead of it, the cruise jumps and makes me take over and tells me check cruise control. I also have the p0504 code. I'd appreciate an insight into this matter.

 

have you checked the brake pedal switch itself? that is the highest wear item in the system

 

where is it located?

 

Here you go.

 

ah btw, how can I check if its working? I took it to a shop and they said if the back lights are working then it's fine. Is there a correct way to check it? I dont have a on hand tester or whatever that is.

 

They are correct as it is just a switch and if brake light is coming on it is working. Have you tried clearing the code by disconnect battery? Could be intermittent switch or wiring.

 

nope doesn't work, tried that. and tried to remove codes from obd but doesn't work. Brake lights do work but cruise control is still janky

 

There are 2 switches as shown in the diagram posted above.
The Stop Light switch is quite separate from the Brake Pedal Load Sensing switch.
The Stop Light switch activates the brake lights when you hit the pedal and if the Cruise is enabled it will cancel Cruise control mode.

The Brake Pedal Load Sensing switch only switches if you press the pedal with more than 59N amount of force and is connected to the skid control ECU.
There is a section on it in the Factory Repair Manual - DTC C1267/67: BRAKE PEDAL LOAD SENSING SWITCH

From the effects and the codes I would suspect the Brake Pedal Load Sensing switch needs replacing, or the wiring/connector to it is damaged.
You can't replace the switch itself so will need to replace the Brake Pedal Sub-Assembly 47106-50010.

 

There are two circuits/switches inside the stop light switch, 4 wires. The brake lights use one switch, the PCM uses the other switch, this is how the computer determines the A/B correlation fault.

Replace the stop light switch.