P0572 Code: Brake Switch A Circuit Low Diagnosis
P0572 Code: Check the Brake Lights Before Buying a Switch
The low input may come from switch adjustment, a missing feed, a short to ground or a failed switch. It can affect cruise control and shift interlock logic.
P0572 = Brake Switch A Circuit Low. P0572 means the control module sees brake switch A voltage lower than expected. Verify all brake lamps, the fuse, switch adjustment and both brake-switch channels before replacing the switch.
What Does P0572 Actually Mean?
P0572 is a low-input fault for brake switch A. The switch may provide more than one signal to the PCM, ABS, body controller and shift-interlock system. A low signal can mean the pedal is interpreted incorrectly or the circuit never receives its supply.
The free first test is to watch every brake lamp, but working lamps do not always prove both switch channels are correct. Compare the scanner’s brake-switch PIDs with pedal movement and verify the electrical circuit at the switch.
Always use the service information for the exact VIN; thresholds and test sequences differ by manufacturer.
Symptoms of P0572
Treat this as a safety fault before driving.
Switch adjustment or a second channel may be involved.
The PCM cannot trust the brake input.
Some interlocks rely on the same switch.
Modules may disagree about pedal state.
One redundant channel can fail while lamps still work.
What Causes P0572? (Ranked Cheapest First)
The labels and order below are diagnostic weightings for test sequence, not published failure-rate statistics. Vehicle design, mileage and companion codes can change the ranking.
Misadjusted or failed brake switch (30% diagnostic weighting)
The plunger does not change channel A correctly.
How to prove it: Compare switch PIDs and test signal voltage through pedal travel.
$15-$120Blown stop-lamp fuse or missing feed (20% diagnostic weighting)
The switch cannot produce a high signal.
How to prove it: Test voltage on both sides of the loaded fuse.
$2-$80Short to ground or damaged harness (20% diagnostic weighting)
The signal is held low.
How to prove it: Unplug the switch and trace whether the signal recovers.
$20-$450Connector terminal problem (10% diagnostic weighting)
Loose or corroded pins create an intermittent low input.
How to prove it: Inspect pin tension and perform a wiggle test on live data.
$10-$250Incorrect bulbs or lamp circuit fault (10% diagnostic weighting)
Shared circuit loading can distort some designs.
How to prove it: Verify approved bulbs and lamp-ground voltage drop.
$10-$200Module input or calibration fault (10% diagnostic weighting)
Rare after switch and wiring tests.
How to prove it: Verify the signal at the receiving module pin.
$0-$1,800What You'll Need
Diagnostic tools
- Full-system scan tool with live data and active tests
- Digital multimeter with back-probes
- Fused jumper leads
- Vehicle wiring diagram and connector views
- Test light or low-current probe where approved
Possible parts and supplies
- Connector cleaner and terminal tools
- Automotive wire and sealed splices
- Correct fuse or relay after testing
- Replacement component only if the circuit proves it faulty
iCarzone UR1000 Bidirectional Scan Tool with ECU Coding
Use the UR1000 to save P0572 freeze-frame data, scan companion modules, graph the relevant command and feedback, and run supported active tests. Confirm electrical values with a meter before replacing parts.
How to Diagnose P0572 at Home
-
1
Save the complete scan report
Record P0572, status, freeze-frame values and every companion code before clearing memory. The companion code often identifies the affected side or prerequisite failure.
- Scan all modules, not only the engine controller.
- Record battery voltage and operating conditions.
- Note recent repairs, low-voltage events and intermittent symptoms.
- Do not erase evidence before duplicating the fault.
-
2
Confirm the exact component and layout
Find the correct switch at the pedal and identify channel A, supply, ground and any redundant brake signal. Some switches self-adjust when installed.
- Use the VIN-specific wiring diagram and component locator.
- Verify bank, sensor, solenoid or circuit labels before unplugging anything.
- Inspect nearby heat, fluid and collision damage.
- Check connectors for water, corrosion, spread terminals and poor locks.
-
3
Check the inexpensive basics
Check every brake lamp, the stop-lamp fuse, bulb sockets and pedal return. Verify the switch is seated and adjusted; do not rotate a self-adjusting switch unless the procedure specifies it.
- Verify battery and charging voltage are stable.
- Inspect related fuses, grounds, hoses, fluid or mechanical linkages.
- Repair obvious damage before condemning an electronic part.
- Re-scan after restoring any shared power or ground fault.
-
4
Use live data or an active test
Watch brake switch A, brake switch B and cruise-cancel PIDs while slowly pressing the pedal. They should change cleanly and correlate as service information specifies.
- Graph the relevant command and feedback PIDs together.
- Change one condition at a time and watch for a plausible response.
- Run a supported output test only when the vehicle is safe and stationary.
- Compare left/right or bank-to-bank data when the design permits.
-
5
Prove the circuit or system under load
Back-probe supply and signal voltage with the switch connected. A low signal with good feed may indicate the switch; a missing feed or grounded wire requires circuit repair.
- Back-probe without spreading terminals.
- Use voltage-drop or current testing instead of an unloaded continuity check.
- Follow the factory limits for the exact module and component.
- Replace the part only when power, ground, command and response point to it.
-
6
Repair, reset and verify
Adjust or replace the proven fault, confirm lamps and shift interlock, then road-test cruise cancellation in a safe area.
- Clear codes only after the repair is complete.
- Perform any required relearn, adaptation or bleed procedure.
- Repeat the original enable conditions while logging data.
- Confirm P0572 and the companion codes do not return.
Safety: Never bypass the brake switch to defeat a shift interlock. The switch is part of the vehicle’s safety logic.
How Much Does P0572 Cost to Fix?
| Repair | DIY Cost | Shop Cost | Notes | Type |
|---|---|---|---|---|
| Connector clean or terminal repair | $0-$40 | $80-$220 | Inspect first | DIY/Inspect |
| Fuse or relay | $8-$60 | $90-$250 | Test before replacing | DIY/Inspect |
| Harness repair | $15-$100 | $150-$650 | Depends on access | DIY/Inspect |
| Sensor, switch or solenoid | $25-$250 | $180-$650 | Code-specific part | DIY/Inspect |
| Module software update | N/A | $0-$250 | VIN-specific | Shop |
| Control module replacement/programming | N/A | $700-$2,500 | Last resort | Shop |
Prices are broad U.S. estimates for July 2026. Labor rate, access and parts availability can move the final bill substantially.
Which Vehicles Commonly Report P0572?
| Make / Model | Years | Powertrain | Diagnostic Notes | Focus |
|---|---|---|---|---|
| Domestic cars and light trucks | Varies by model | brake-light, cruise-control and interlock input | Confirm the brake switch A circuit layout and code enable criteria by VIN. | High |
| European vehicles | Varies by model | brake-light, cruise-control and interlock input | Factory code text may add a manufacturer-specific suffix or test threshold. | Medium |
| Asian vehicles | Varies by model | brake-light, cruise-control and interlock input | Connector pinout and active-test support differ by platform. | Medium |
| Hybrids or electrified variants | When equipped | brake-light, cruise-control and interlock input | Do not assume the non-hybrid test plan applies to high-voltage hardware. | Lower |
| Older high-mileage vehicles | Age dependent | brake-light, cruise-control and interlock input | Corrosion, fluid intrusion and harness fatigue deserve extra attention. | Medium |
| Recently repaired vehicles | Any year | brake-light, cruise-control and interlock input | Recheck disturbed connectors, grounds, hoses and software history first. | High |
Why working brake lights are not enough
Many vehicles use redundant contacts or distribute the brake signal through several modules. The lamp circuit can work while the PCM-facing channel remains low.
Switch adjustment after installation
Some pedal switches set their own plunger position during installation. Reusing or twisting one incorrectly can create P0572 even when the new part is electrically good.
Should You DIY or Call a Mechanic?
- ✓ The vehicle remains safe and stable while testing.
- ✓ You can identify the correct component from a wiring diagram.
- ✓ The checks are limited to accessible connectors, hoses, fuses or live data.
- ✓ No programming, high-voltage work or internal mechanical repair is required.
- → The vehicle stalls, overheats, misfires severely or enters a harsh limp mode.
- → High voltage, fuel pressure or internal transmission work is involved.
- → The circuit reaches an inaccessible module connector.
- → Programming, oscilloscope work or manufacturer tooling is required.
Frequently Asked Questions
What does P0572 mean?
Can I drive with P0572?
What is the most common first check for P0572?
Does P0572 always mean the brake switch A circuit is bad?
How does the iCarzone UR1000 help?
Should I clear P0572 first?
Can a weak battery create this code?
How do I confirm the repair?
This article is for informational purposes only. Always follow the factory service manual, safety procedures and local emissions rules for the exact vehicle. iCARZONE is not responsible for damage caused by improper diagnosis or repair.