What it means
Brake Switch B Circuit Low: the signal voltage is below the expected range. Often a short to ground or high resistance in the wiring.
At a glance
- Usually lights the check-engine light
How it works
Brake switch B provides a brake pedal status signal used by vehicle controls, including transmission logic on some vehicles. P0719 sets when the switch B circuit signal stays below its expected electrical range, which can result from a short to ground, poor contact, or a failed switch.
Common causes
Most likely first.
- Brake switch defective
- Wiring shorted to ground
- Connector pins corroded - high contact resistance
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Check whether the brake lamps work consistently and compare brake switch B's live status with pedal position using a scan tool.
- Inspect the brake switch B connector and nearby wiring for corrosion, loose pins, damage, or contact with ground.
- Use the manufacturer's wiring diagram to test the switch B circuit for a short to ground, an open, or excessive resistance.
- Check switch adjustment and verify that its signal changes as the pedal is pressed and released, following the manufacturer's procedure.
- If the circuit and adjustment are sound, test or replace the brake switch as indicated by the specified test.
Common fixes
- Clean and secure the brake switch B connector if terminals have poor contact.
- Repair wiring shorted to ground or damaged in the switch B circuit.
- Adjust the brake switch if it is mispositioned and the manufacturer's procedure allows adjustment.
- Replace the defective brake switch if its signal remains low despite a sound circuit.
Can I keep driving?
Before driving, confirm the brake lamps work; do not drive if they fail or stay on, since other road users may not see your braking. If braking feels normal and the lamps operate, drive cautiously to have the fault diagnosed because transmission behavior or cruise functions may be affected.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.