What it means
Brake Switch B Circuit High: the signal voltage is above the expected range. Often an open circuit or a short to supply voltage.
At a glance
- Usually lights the check-engine light
How it works
Brake switch B provides a brake-pedal signal to the vehicle's control modules, which may use it for functions including transmission shift control. P0724 sets when the module detects switch B's circuit voltage above its expected range, which can happen with an open circuit or a short to supply.
Common causes
Most likely first.
- Brake switch defective
- Wiring open
- 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
- Read freeze-frame data and live brake-switch B status to see whether the module reports the brake applied or released incorrectly.
- With the vehicle parked, press and release the brake pedal while checking switch B data and confirming that the brake lamps respond normally.
- Inspect the brake switch connector and wiring for a loose plug, corrosion, damaged insulation, or an open circuit.
- Check switch adjustment and whether the pedal reliably actuates it throughout its travel.
- Use the wiring diagram to test switch B's signal circuit for an open or short to supply and verify switch operation against the manufacturer's specification.
Common fixes
- Reconnect or clean corroded brake switch B terminals.
- Repair an open or damaged brake switch B wire.
- Repair wiring shorted to supply voltage.
- Adjust or replace the brake switch if it fails to change state correctly.
Can I keep driving?
Confirm the brake lamps work before driving; if they do not, do not drive in traffic because other drivers may not see you braking. Transmission shifts may also be affected, so arrange repair promptly.
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.