P0573 is a diagnostic trouble code that points to a problem in your cruise control/brake switch circuit, usually described as “Brake Switch A Circuit High.” In plain language, your car’s computer is seeing an electrical signal from the brake pedal that doesn’t make sense. This can disable cruise control and sometimes trigger warning lights. While it’s not usually a safety emergency, it can affect brake lights and driver assist systems on newer cars. Understanding what this code means, how it behaves, and how to fix it will save you time, money, and frustration.
What Does P0573 Mean?
P0573 is a generic OBD-II code that indicates the powertrain control module (PCM/ECU) has detected an abnormally high voltage signal in the “A” circuit of the brake pedal switch, which is closely tied to the cruise control system. The ECU expects the signal to change when you press and release the brake; when the voltage stays too high or out of range, it sets P0573.
Because the brake switch is used for more than just cruise control (it often feeds brake lights, shift interlock, and stability control), this code can affect several systems. In most cases, the root cause is a faulty brake pedal switch, wiring issue, or misadjusted switch.
Quick Reference
- Code: P0573 – Brake Switch A Circuit High
- System: Cruise control / brake pedal input
- Severity: Low to moderate (safety concern if brake lights affected)
- Most common cause: Failed or misadjusted brake pedal switch
- Typical fix: Replace or adjust brake switch, repair wiring or connector
Real-World Example / Field Notes
In the shop, I see P0573 most often on vehicles where the owner complains that cruise control stopped working, but the car otherwise drives fine. On some models, the customer also notices that the brake lights stay on even when the pedal isn’t pressed, or they flicker. A quick scan shows P0573 stored, sometimes along with ABS or traction control codes. Nine times out of ten, a worn brake switch or corroded connector at the brake pedal is to blame, and replacing the switch restores normal operation.
Symptoms of P0573
- Cruise control inoperative – Cruise won’t set or drops out immediately.
- Brake lights staying on – Rear brake lamps may stay illuminated after you release the pedal.
- Brake lights not working correctly – In some cases, brake lights may not come on when pressing the pedal.
- Warning lights on dash – You may see ABS, traction control, or stability control warning lamps.
- Check engine light (MIL) – The CEL or service engine soon light may turn on and store P0573.
- Transmission shift interlock issues – Difficulty shifting out of Park on some automatic transmissions.
- Intermittent cruise engagement – Cruise works sometimes, then suddenly cancels or refuses to set.
Common Causes of P0573
Most Common Causes
- Failed or worn brake pedal switch (internal contacts burned or stuck).
- Misadjusted brake switch not properly contacting the pedal, causing incorrect signal.
- Corroded or loose connector at the brake switch, especially in humid or salty climates.
- Broken or chafed wiring in the harness near the brake pedal area.
- Aftermarket accessories (remote start, alarm, trailer wiring) spliced into the brake light circuit incorrectly.
Less Common Causes
- Faulty cruise control module or body control module (BCM) on vehicles that route the signal through these units.
- ECU/PCM internal fault misreading the brake switch signal (rare, but possible).
- Water intrusion into the dash or footwell area causing intermittent shorts or high resistance.
- Incorrect replacement switch installed (wrong part number or pin configuration).
- Mechanical pedal issues such as a bent pedal bracket preventing proper switch contact.
Diagnosis: Step-by-Step Guide
Basic tools you’ll want: an OBD-II scan tool (preferably with live data and Mode $06), a digital multimeter, a test light, and simple hand tools to access the brake pedal area. A wiring diagram for your specific vehicle is very helpful.
- Confirm the code. Use a scan tool to read codes. Note if P0573 appears alone or with other brake, ABS, or cruise control codes. Clear the codes and see if P0573 returns immediately or only after driving.
- Check brake light operation. With the ignition on, verify if the brake lights come on when pressing the pedal and turn off when released. Stuck-on or non-functioning lights point directly toward a switch or adjustment issue.
- Inspect the brake switch and bracket. Look above the brake pedal for the switch. Check for physical damage, loose mounting, or a pedal that doesn’t fully contact the switch plunger. Make sure nothing is obstructing the pedal travel.
- Check the connector and wiring. Unplug the switch and inspect the connector for corrosion, bent pins, or moisture. Gently tug the wires to see if any are broken inside the insulation, especially where the harness flexes.
- Test power and ground at the switch. With a multimeter or test light, verify that you have proper battery voltage and ground at the correct pins according to the wiring diagram. No power or ground means you need to trace the circuit back toward the fuse or BCM.
- Test switch output. With the switch plugged in (back-probed) or on the bench, monitor the output wire while pressing and releasing the brake pedal. The voltage should switch cleanly between specified states (usually near 0 V and near battery voltage). A signal that stays high or flickers can trigger P0573.
- Use scan tool live data. Many scan tools show “Brake Switch” or “Brake Pedal Position” status. Watch this PID while gently pressing and releasing the pedal. If the ECU still sees “ON” when the pedal is released, the code makes sense and the switch or wiring is suspect.
- Check for aftermarket wiring. Look for add-on modules, trailer brake controllers, or remote starts tied into the brake circuit. Poor splices or Scotch-lock connectors can cause high resistance or false signals.
- Perform continuity checks. If needed, disconnect the ECU and brake switch, then check continuity and resistance of the circuit wires end to end. High resistance or open circuits must be repaired.
- Re-test after each repair. After replacing or adjusting the switch, clearing corrosion, or repairing wiring, clear the code and test drive. Monitor live data to confirm the brake signal behaves normally.
Pro tip: On many vehicles, a brand-new brake switch still needs proper adjustment. If you just bolt it in without setting the plunger position against the pedal correctly, you can still end up with P0573 or brake lights that behave oddly.
Possible Fixes & Repair Costs
Most repairs for P0573 are straightforward and not extremely expensive. A typical brake pedal switch replacement at a shop can range from about $75–$250 total, including parts and labor, depending on vehicle design and labor rates. Wiring repairs can range from $100–$300 if harness work is needed. In rare cases where a BCM or ECU is at fault, you may see costs from $400 up to $1,000+ due to programming and module prices. Final cost depends on parts availability, dealer vs. independent shop, and how difficult the switch is to access.
- Replace faulty brake pedal switch.
- Adjust brake switch position and pedal stop.
- Clean or replace corroded electrical connectors.
- Repair or replace damaged wiring in the brake switch circuit.
- Remove or correct poorly installed aftermarket wiring.
- In rare cases, replace and program BCM/ECU if confirmed faulty.
Can I Still Drive With P0573?
In most cases, you can still drive with P0573 without immediate danger, but you should verify that your brake lights work correctly before going anywhere. If the brake lamps stay on or don’t come on at all, that’s a safety issue and could get you rear-ended or ticketed. You’ll likely lose cruise control and possibly some driver-assist features. Treat it as a “drive to the shop soon” situation, not an emergency tow, unless the brake lights are clearly malfunctioning.
What Happens If You Ignore P0573?
If you ignore P0573, you risk driving with unreliable brake light operation and disabled cruise control or stability systems. Over time, a stuck-on brake light can drain your battery. On newer vehicles, the ECU may also limit certain functions if it can’t trust the brake switch signal. It’s a relatively inexpensive problem to fix, so it’s best not to put it off.
Related Codes
- P0574 – Cruise Control System Vehicle Speed Too High
- P0572 – Brake Switch “A” Circuit Low
- P0571 – Brake Switch “A” Circuit
- P0570 – Cruise Control Accelerate Signal
- P0569 – Cruise Control Coast Signal
- P0568 – Cruise Control Set Signal
- P0567 – Cruise Control Resume Signal
- P0566 – Cruise Control Off Signal
- P0565 – Cruise Control On Signal
- P0564 – Cruise Control Multi-Function Input “A” Circuit
Key Takeaways
- P0573 means the ECU sees an abnormally high signal from the brake switch “A” circuit.
- The most common culprit is a faulty or misadjusted brake pedal switch or its wiring.
- Symptoms usually include inoperative cruise control and possible brake light issues.
- Diagnosis focuses on checking switch operation, wiring, and live data from the ECU.
- Repairs are often affordable and should be done soon for safety and convenience.
Vehicles Commonly Affected by P0573
P0573 is a generic OBD-II code, so you can see it on many makes and models. It’s especially common on mid-2000s and newer vehicles from manufacturers like Ford, Chevrolet, GMC, Dodge/Ram, Chrysler, Toyota, Honda, Hyundai, Kia, Volkswagen, and Subaru. You’ll often see it on sedans and compact cars with heavy daily use, as well as SUVs and pickup trucks that see a lot of stop-and-go driving. Any vehicle with electronic cruise control and a shared brake switch circuit can set this code when the switch or wiring starts to fail.
FAQ
Can P0573 cause my brake lights to stop working?
Yes. P0573 indicates the ECU is seeing an abnormal brake switch signal, and that switch often controls your brake lights. Depending on how it fails, the lights may stay on constantly, not come on at all, or work intermittently. Always verify brake light operation when this code appears.
Is P0573 dangerous to drive with?
It can be, if your brake lights are affected. If the lights don’t work correctly, other drivers can’t see when you’re slowing down, which is a serious safety risk. If the lights work normally and only cruise control is disabled, the risk is lower, but you should still repair it soon.
How do I know if the brake switch is bad or just misadjusted?
If the switch tests electrically good but the brake lights come on too early, stay on, or don’t respond until the pedal is nearly on the floor, it’s often an adjustment issue. If the switch output is erratic or doesn’t change when you move the pedal, even when properly positioned, the switch itself is likely bad.
Can I replace the brake switch myself?
On many vehicles, yes. The brake switch is usually mounted near the top of the brake pedal and held with a clip or threaded nut. If you’re comfortable working under the dash and following basic instructions, you can often replace it at home. Just be sure to adjust it correctly and verify brake light operation afterward.
Does clearing P0573 with a scanner fix the problem?
No. Clearing the code only erases it from the ECU’s memory temporarily. If the underlying issue with the brake switch circuit remains, P0573 will return once the ECU runs its checks again. You need to repair the cause—switch, wiring, or adjustment—before clearing the code will have any lasting effect.