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Severity: Moderate Code type: Generic (all makes)

P0572 Code: Brake Switch A Circuit Low

The PCM never sees the brake pedal pressed – brake lights may be out and the car may not shift or start.

Safety first · Consult a professional

  • Braking system affected: ABS may be disabled. Drive carefully and have it checked promptly.

At a glance

Severity: 3/5 – Moderate3/5

Severity: Moderate

Meaning
Brake Switch A Circuit Low
System
Speed & Idle Control · Powertrain
Safe to drive?
With caution
Typical repair cost
$5–$350
DIY difficulty
Easy

P0572 sets when the brake switch A input stays low, meaning the PCM sees 'pedal released' even when the car is braked to a stop. On most vehicles this circuit gets battery voltage through the stop lamp fuse, passes through the switch when the pedal is pressed and feeds both the brake lights and the PCM. If the fuse has blown, the switch no longer closes, or the feed wire is broken, the voltage never arrives. That has safety consequences beyond cruise control: the brake lights may not come on at all, the shifter may stay locked in Park and a push-button start may refuse to crank because it can't detect the pedal.

Can I keep driving? Check the brake lights before driving. If they don't light, don't drive in traffic, since following drivers get no warning when you stop; get the fuse or switch fixed first.

How to read P0572

How to read P0572P10253724
  1. P Powertrain
  2. 0 Generic (SAE)
  3. 5 Speed, idle & inputs
  4. 72 Specific fault

Symptoms

  • Brake lights don't come on at all when the pedal is pressed
  • Shifter won't come out of Park
  • Push-button start only goes to accessory mode and won't crank
  • Cruise control won't engage
  • Traction, stability or ABS warning light on
  • Hazard lights or turn signals also dead on vehicles where they share the fuse

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Blown stop lamp fuse, often from a short in trailer wiring or the rear lamp harness 30%
  2. Brake switch failed open and no longer closes when pressed 28%
  3. Switch misadjusted or its bracket broken so it never activates 14%
  4. Broken feed wire or loose connector at the switch 14%
  5. Faulty trailer tow module or aftermarket lighting pulling the circuit down 8%
  6. PCM or body module input fault 6%

Diagnosis step by step

Diagnostic flow: P05721Check the brake lights and stop lampfuse2Hunt the short if the fuse blows3Check power at the switch4Check the output with the pedalpressed5Confirm the PCM sees the change

  1. Check the brake lights and stop lamp fuse

    With the key on, press the pedal and check the lights. If none light, find the stop lamp fuse in the owner's manual and test it; a blown fuse needs a cause, so don't just fit a larger one.

    Tools: Flashlight, Multimeter

  2. Hunt the short if the fuse blows

    Common spots are the trailer socket and tow module, the harness where it passes through the trunk or hatch hinge, and the third brake light wiring. Disconnect the trailer wiring and check the hinge area for pinched or bare wires.

    Tools: Flashlight, Multimeter

  3. Check power at the switch

    Back-probe the switch connector: one terminal should have battery voltage at all times (or with the key on, depending on design). If there's no voltage there with a good fuse, the feed wire is open between the fuse box and the pedal.

    Tools: Multimeter

  4. Check the output with the pedal pressed

    With the pedal pressed, the switch output terminal should show nearly the same voltage as its input. Voltage in but not out means the switch isn't closing, either worn out or held open by bad adjustment.

    Tools: Multimeter

  5. Confirm the PCM sees the change

    On the scan tool, the brake switch status should change from 'released' to 'applied' as soon as the pedal moves. If voltage reaches the PCM connector but the status never changes, the PCM input is suspect, which is rare.

    Tools: OBD-II scanner

Where the parts are

Ignition: coils and spark plugs per cylinder – P05721234567
Ignition: coils and spark plugs per cylinder
  1. 1Ignition coil
  2. 2Spark plug
  3. 3Fuel injector
  4. 4Camshaft sensor
  5. 5Crankshaft sensor
  6. 6Engine computer (ECM)
  7. 7Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Replace stop lamp fuse (after finding the short) Yes $5–$150
Replace and adjust brake switch Yes $50–$180
Repair pinched harness in trunk or hatch hinge No $100–$350
Replace trailer wiring connector or tow module No $60–$300

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Emissions / smog test impact

Depends

Emissions tests only fail P0572 if it turns on the check engine light, which varies by vehicle. In states with safety inspections, non-working brake lights are an automatic failure and a reason to be pulled over.

Frequently asked questions

My car won't shift out of Park. Is the transmission broken?

Very likely not. The shift interlock only releases when the brake signal arrives. Most vehicles have a small shift-lock release slot near the shifter for emergencies; fixing the brake switch circuit restores normal operation.

Why does my push-button start only turn on the radio?

Push-button start needs to see the brake pedal pressed before it will crank the engine. With P0572 that signal is missing, so the system stays in accessory mode.

I replaced the fuse and it blew again. What now?

Something in the brake light circuit is shorted to ground. Check the trailer wiring first, then the harness through the trunk or hatch hinges and the third brake light; unplugging sections one at a time narrows it down.

Can I drive without brake lights until I get parts?

It isn't safe and it's illegal. Drivers behind you have no warning when you slow down, which is a classic cause of rear-end collisions.

Sources