01 Understanding the Engine Block: A Comprehensive Guide • 02 What Causes a Starter Motor to Turn Slowly and Fail to Star… • 03 Mechanic's Secret: The Foolproof Way to Identify Oxygen Sen… • 04 Steering Wheel Feels Loose? Uneven Tire Wear? Don't Ignore … • 05 Why Did Jaguar Land Rover Suddenly Stop Shipping Cars to th… • 06 From Manifold to Tailpipe: How Exhaust System Components Bo… • 07 When Reconnecting The Battery, Which Terminal is Connected … • 08 This Is Why Your Car’s Engine Oil Turns Black So Fast • 09 The Best Oil for Older Diesel Engines: Buyer's Guide • 10 Inline vs V Engine: Pros, Cons, Power, and Fuel Efficiency •

DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P0572

P0572Brake Switch 'A' Circuit Low

P0572 means the engine computer has detected a low-voltage condition on the brake pedal switch 'A' signal circuit, which is the primary input used to release the torque converter clutch and disengage cruise control. The computer expects to see battery voltage on this circuit when the brake pedal is released, and it sets this code when the voltage stays below the threshold for a calibrated amount of time.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The cruise control will not engage or drops out as soon as you press the brake pedal
  • The torque converter clutch may stay locked when you brake, causing the engine to shudder or stall as you come to a stop
  • The brake lights may be dim, inoperative, or stuck on depending on how the switch fails
  • A warning light on the dashboard and a stored P0572 code in the engine computer
  • Often no symptoms besides the warning light, because the brake lights themselves may still work through a separate switch contact
  • On some vehicles the engine may hesitate or idle poorly when the brake pedal is pressed because the computer cannot confirm the brake input

Common causes, most likely first

  1. A failed or misadjusted brake pedal position switch, which is the most common cause of this code
  2. A blown fuse that feeds the brake switch circuit, often shared with the brake lights or cruise control
  3. Corroded, loose, or damaged wiring and connectors between the brake switch and the engine computer
  4. A short to ground on the signal wire, which pulls the voltage low even when the switch is closed
  5. A faulty brake switch ground connection at the pedal bracket or chassis
  6. A defective engine computer, which is rare but possible after all other causes are ruled out
  7. Aftermarket accessories tapped into the brake light circuit that draw down the signal voltage

How to diagnose and fix it

  1. Check all fuses related to the brake lights and cruise control, and replace any that are blown
  2. Inspect the brake pedal switch for proper adjustment and listen for the click of the switch as the pedal moves
  3. Disconnect the brake switch connector and check for battery voltage on the feed circuit with the key on
  4. Measure resistance on the ground circuit from the brake switch to the chassis and repair any high resistance
  5. Back-probe the signal wire at the engine computer and compare voltage with the brake pedal released and pressed
  6. Repair any chafed, corroded, or shorted wiring between the switch and the computer, then clear the code and retest
  7. Replace the brake pedal switch if it fails the voltage and continuity tests, then verify the code does not return

Why brake switch codes fool good technicians

  • Many vehicles use a dual-contact brake switch where one contact feeds the brake lights and the other feeds the computer, so the brake lights can work perfectly while the computer still sets P0572.
  • A misadjusted switch that is not fully depressed when the pedal is released will keep the signal circuit low and set this code even though the switch itself is electrically good.
  • Aftermarket LED brake light bulbs or trailer wiring harnesses can back-feed the brake signal circuit and cause a low-voltage condition that mimics a failed switch.
  • The code can be set by a weak battery or charging system problem that drops system voltage below the threshold during cranking, so always check battery health before replacing parts.
  • On some vehicles the brake switch signal is shared with the shifter interlock or stability control system, so a fault in those circuits can pull the brake signal low and set P0572.

Can I keep driving with P0572?

You can usually drive the vehicle, but avoid using cruise control and be aware that the torque converter clutch may not release properly, which can cause stalling during braking. Have the fault diagnosed soon, especially if the brake lights are not working correctly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage