P0724 code meaning
Brake Switch B Circuit High
What P0724 means
Brake switch B is the brake signal to the transmission module or a second brake switch channel, used to release the converter clutch, adapt shift strategy on grades and cancel cruise control. Low and high describe the signal voltage, and what that means depends on polarity: GM's converter clutch brake switch is closed at rest (12 V), while Saab's Trionic 8 sees 12 V when braking. Detection is always a plausibility check against driving: the brake reads applied during accelerations or never applied during decelerations. P0724 means the signal stays high. For GM that reads as brake never applied: 2006 transmission modules flag it after eight decelerations without a brake signal of at least 2 s, without MIL. Saab's Trionic 8 flags a brake light signal that reads on while accelerating from 3 to 40 km/h, four times, and disables cruise control. The opposite is P0719.
P0724 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0724
- Cruise control cannot be activated or switches off
- Unusual shifting, converter clutch behaviour changed
- No downshift on uphill grades (Subaru)
- Brake lights stay off or on
Common causes of P0724
- Most likelyBrake light switch sticking or misadjusted
- PossibleSignal wire shorted to positive (Saab T8) or switch permanently closed (GM)
- Less likelyRetrofitted trailer or LED lights feeding back
- Less likelyModule input faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake switchBrake switch wiringTransmission control module
What each part of P0724 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7 | Area: transmission. |
| 24 | The exact fault in that area. |
What to do next
- Note P0724 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0724
What does P0724 mean?
P0724 means "Brake Switch B Circuit High". Brake switch B is the brake signal to the transmission module or a second brake switch channel, used to release the converter clutch, adapt shift strategy on grades and cancel cruise control. It is a generic code, so it means the same on every make.
Is it safe to drive with P0724?
P0724 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0724 fail an emissions test?
P0724 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0724 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0724 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.