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P0572 — Brake Switch Circuit Low

Generic OBD-II · all makesPowertrain (engine & transmission)

P0572 indicates the powertrain control module (PCM) has detected a low-voltage signal on the brake switch 'A' circuit. The brake (stop lamp) switch tells the PCM when the pedal is pressed, so a low reading typically means the circuit is shorted, the switch is faulty, or the signal is not being sent as expected.

Symptoms

What causes it — most likely first

1. Failed brake light / stop lamp switch

The switch itself is a wear item and the single most common cause. Internal contacts wear out, stick, or short, producing a low or absent signal to the PCM.

2. Wiring short to ground in the brake switch circuit

Chafed, pinched, or melted wiring between the switch and the PCM can pull the signal voltage low. Common in areas near the pedal bracket or firewall pass-through.

3. Corroded, loose, or damaged connector at the brake switch

Moisture intrusion or repeated pedal movement can loosen the connector or corrode the terminals, creating a high-resistance or shorted path.

4. Poor chassis or PCM ground

A weak or corroded ground shared with the brake switch circuit can cause the reference voltage to read abnormally low to the PCM.

5. Faulty brake light relay or associated fuse fault

On vehicles that route the brake signal through a relay, a sticking relay or a partially failed fuse can drop circuit voltage and set this code.

6. PCM / ECM internal failure

The engine computer itself is an uncommon cause of P0572. It is generally only considered after the switch, wiring, connectors, and grounds have all been verified good.

How it's diagnosed

  1. Verify the symptom: have an assistant press the brake pedal and confirm whether the brake lamps illuminate normally, stay on, or fail to light.
  2. Connect a scan tool and check live data for the brake switch status; confirm whether the PCM sees the pedal pressed and released as expected.
  3. Unplug the brake switch connector and inspect the terminals for corrosion, bent pins, or pushed-back weather seals. Repair or clean as needed before further testing.
  4. Test the brake switch with a multimeter: check for continuity when the pedal is pressed and an open circuit when released, and check for a short to ground across the switch terminals.
  5. With the switch disconnected, back-probe the harness side to check for proper reference voltage and ground at the PCM, and inspect the wiring for shorts to ground or opens.
  6. Only after the switch, wiring, connector, and grounds are verified should the PCM be considered as a possible cause.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make
Related codesP0570 — Cruise Control Accelerate SignalP0571 — Brake Switch CircuitP0573 — Brake Switch Circuit HighP0574 — Cruise Control System Vehicle Speed P0575 — Cruise Control Input CircuitP0576 — Cruise Control Input Circuit Low

Frequently asked

Is it safe to drive with P0572?

Usually the vehicle will still run and drive, but features that depend on the brake signal such as cruise control, push-button start, and proper torque converter lockup may not work correctly. Address it promptly because inop brake lights are a safety and legal issue.

Will replacing the PCM fix P0572?

Almost never. P0572 is a sensor and wiring code, and the vast majority of cases are caused by the brake switch itself, the connector, or the wiring. The PCM is replaced for this code only in rare instances after every other cause has been ruled out.

Why do my brake lights stay on with this code?

A shorted switch or wiring can keep the brake signal circuit active even when the pedal is released, leaving the brake lamps illuminated. The stuck-on signal also confuses the PCM and sets the code.

Can a bad brake switch drain the battery?

Yes. If the switch is stuck in the closed position, the brake lamps can remain lit whenever the ignition is on, which over time can discharge the battery.