OBD-II Code P0572: What It Is, Symptoms, Causes & How to Fix It with iCarsoft CR MAX BT

If your vehicle’s check engine light illuminates, your brake lights fail to work, or your cruise control won’t engage with OBD-II Code P0572—defined as Brake Switch 'A' Circuit Low—you’re facing a safety-critical electrical fault in your vehicle’s brake system. The Brake Switch 'A' is the primary brake light switch mounted to your brake pedal, and a “circuit low” error means its electrical voltage falls far below the Engine Control Module (ECM)’s expected range. This small switch controls critical systems: brake lights, cruise control disengagement, automatic transmission shift lock, and even regenerative braking in hybrids/EVs. Left unaddressed, P0572 creates dangerous driving hazards (e.g., unlit brake lights) and disables key vehicle features. But you don’t need to pay steep dealer diagnostic fees for a simple brake switch issue: this guide breaks down everything you need to know about P0572, plus why the iCarsoft CR MAX BT diagnostic tool is the DIYer’s ultimate solution to detect, troubleshoot, and clear this error code with professional precision—no advanced electrical skills required.

What Is OBD-II Code P0572?

OBD-II codes are the ECM’s universal alert system for powertrain and electrical malfunctions, and P0572 zeroes in on a low-voltage fault in the primary Brake Switch 'A' circuit—a foundational component of your vehicle’s brake and electrical safety systems. Here’s a clear, jargon-free breakdown:

• Brake Switch 'A': The main brake light switch mounted directly above the brake pedal in the driver’s footwell. It’s a normally open switch that closes when you press the brake pedal, sending an electrical signal to the ECM to activate brake lights, disengage cruise control, and release the automatic transmission’s shift lock (so you can move the gear selector from Park).
• Circuit Low: The electrical voltage in the Brake Switch 'A' circuit drops below the manufacturer’s pre-set minimum threshold (typically 0-1V when it should be 12V). This means the ECM is not receiving a valid signal from the switch—either the switch is faulty, the circuit has a break/short, or power to the switch is interrupted.
• Dual Switch Note: Most modern vehicles have two brake switches (A and B) for redundancy: Switch A is the primary (ECM/ brake lights), Switch B is the secondary (ABS/ESC/hybrid regenerative braking). P0572 only affects Switch A, but a fault here can still disrupt secondary systems indirectly.
• P0572 is one of the most common brake-related OBD-II codes, and it appears on all 1996+ US, 2000+ EU/Asian OBD-II compliant vehicles—gas, diesel, hybrid, and electric—with automatic transmissions (and many manuals with cruise control). It’s a safety code, not a minor glitch: unlit brake lights increase crash risk, and a stuck shift lock can leave you stranded in Park.

Common Symptoms of P0572

P0572’s symptoms are hard to miss, as they directly impact visible and functional brake system features. The check engine light is the first alert, but you’ll almost always notice one or more of these critical red flags—all of which create driving hazards:

• Illuminated solid Check Engine Light (MIL) on the dashboard
• Brake lights that fail to turn on (the most dangerous symptom—other drivers can’t see when you brake)
• Cruise control that won’t activate, or disengages randomly
• Inability to shift the automatic transmission from Park to Drive/Neutral (shift lock remains engaged)
• Illuminated brake system warning light on the dashboard
• Regenerative braking failure in hybrid/electric vehicles (no energy recovery when braking)
• Delayed or unresponsive brake light activation (in mild circuit low cases)
• Intermittent operation of brake lights/cruise control (from a loose/corroded circuit connection)

Top Causes of P0572

Pinpointing P0572’s root cause is straightforward with the right diagnostic tool, and the fault is almost always a simple electrical issue (not a complex brake system failure). The most common triggers (in order of likelihood—90% of P0572 cases are the first three causes) are:

• Faulty Brake Switch 'A': Internal electrical failure of the switch (the #1 cause) – the switch no longer sends a valid voltage signal when the brake pedal is pressed.
• Corroded/loose Brake Switch 'A' wiring/connector: Rust, dirt, or a loose pin in the switch’s electrical connector disrupts voltage flow, causing a low-voltage signal.
• Broken/shorted circuit wiring: Damaged insulation or a broken wire in the Brake Switch 'A' circuit (from footwell wear/tear or rodent damage) creates a voltage drop.
• Blown brake switch fuse: A blown fuse in the fuse box cuts power to the Brake Switch 'A' circuit, leading to 0V and a P0572 code.
• Incorrect brake switch installation/ adjustment: The switch is misaligned with the brake pedal, so it doesn’t close fully when the pedal is pressed (common after brake pedal/switch repairs).
• Brake pedal position sensor fault: A faulty pedal sensor misinterprets pedal travel, causing the ECM to read a false low-voltage signal from Switch A (indirect cause).
• Low vehicle battery voltage: A weak 12V battery (below 11.5V) reduces voltage to the entire brake switch circuit, triggering P0572.
• ECM signal interpretation fault (extremely rare): The ECM fails to read a valid signal from the switch (only after all other electrical issues are ruled out).

Why the iCarsoft CR MAX BT Is Ideal for P0572

Generic OBD scanners only read the P0572 code—they cannot test the Brake Switch 'A' circuit’s voltage, check switch functionality, or distinguish between a faulty switch and a corroded wire. This leaves many DIYers guessing and replacing parts unnecessarily (e.g., a new switch when the real issue is a blown fuse). The iCarsoft CR MAX BT (bluetooth-enabled, professional-grade) is optimized for automotive electrical and brake system diagnostics, with exclusive features that make it the perfect tool for resolving P0572 quickly and safely. Here’s why it stands out from basic scanners:

Real Customer Reviews: iCarsoft CR MAX BT for P0572

FAQ: Everything You Need to Know About P0572 & iCarsoft CR MAX BT

Final Thoughts: Don’t Let P0572 Compromise Your Brake System Safety

OBD-II Code P0572 is one of the most common and most dangerous electrical fault codes—because it directly impacts your vehicle’s brake light functionality, a core safety feature. Generic OBD scanners leave you guessing and open to unnecessary part replacements, but the iCarsoft CR MAX BT gives you professional-grade brake switch circuit diagnostics to pinpoint the exact cause of P0572 in minutes: a blown fuse, corroded wire, faulty switch, or misaligned mount.

This tool isn’t just a solution for P0572—it’s a critical addition to every driver’s toolbox. It diagnoses all brake system electrical faults, monitors your 12V battery, and reads every other OBD-II code for your engine, transmission, and emissions systems. For a fault as simple (and dangerous) as P0572, the CR MAX BT eliminates the need for expensive dealer diagnostics and lets you fix the issue yourself—safely, quickly, and for pennies on the dollar.

Your brake system is non-negotiable for safety, and P0572 is a warning you can’t ignore. Ready to fix P0572, restore your brake lights/cruise control, and get back on the road safely? Grab the iCarsoft CR MAX BT today and take complete control of your vehicle’s brake switch and electrical safety systems—with wireless convenience and professional diagnostic precision!

Disclaimer: This guide is for informational purposes only. Always consult your vehicle’s service manual or a certified mechanic before brake switch, electrical circuit, or brake system repairs. iCarsoft is not responsible for damage from improper tool use or vehicle maintenance.