P0724 OBD-II Trouble Code: Torque Converter/Brake Switch B Circuit High
P0724 code definition
The P0274 code signifies that the computer has detected a fault in the brake switch B circuit, which includes the cruise control system, and the torque converter.
What the P0724 code means
The P0724 code means that the computer has detected a fault in the brake switch B circuit. This circuit includes the torque converter lock-up system, as well as the car’s cruise control system. When you press the brake pedal, the brake switch operates several circuits. One of those includes the transmission interlock switch, which allows you to shift the transmission out of park. The brake switch B circuit allows the cruise control system to be disengaged by tapping the brake pedal, as well as ensuring that the torque converter lock-up system disengages when coming to a stop.
What causes the P0724 code?
There are only a handful of potential causes for the P0724 code, including the following:
- A failed or faulty brake switch
- A misadjusted brake switch
- Open or short in brake switch harness
- Loose or poor connection in brake switch circuit
- Blown brake light fuse
- Faulty bulb sockets (rare)
What are the symptoms of the P0724 code?
You may experience one or more symptoms when the P0724 code is stored, including the following:
- Brake lights will not turn on
- Brake lights stay on at all times
- Engine stalling when coming to a stop
- Lack of torque converter lock-up
- Check Engine Light on in dash
- Additional codes stored in the computer
How does a mechanic diagnose the P0724 code?
The first step in any diagnosis is to connect an OBD II scanner to the vehicle and check the codes stored. With a P0724 code, chances are good that there are additional codes stored, as well. The brake light fuse should be checked. If it is blown, it must be replaced before further diagnostics can be completed.
Next, the mechanic should check the brake light switch adjustment, as well as the wiring and connectors. If the switch is within adjustment specs and no damage is seen with the wiring, the switch should be tested. If the reference voltage is incorrect (or no voltage is detected), the switch should be replaced. Once the switch has been replaced, the system should be retested. The codes should be cleared and the vehicle should be test driven (and brake light operation should be checked prior to driving the car).
If the problem is not related to the switch, the mechanic will need to inspect the torque converter lock-up solenoid and wiring.
Common mistakes when diagnosing the P0724 code
The most common mistake here is assuming that the problem is with the transmission. In almost all cases, the problem is with the brake light switch, connector, wiring or fuse.
How serious is the P0724 code?
The P0724 code is very serious and will affect the drivability of the car. Depending on the symptoms being experienced, you may be stranded in traffic if the engine stalls while stopping, or you may have no brake lights to tell drivers behind you on the road that you’re slowing down, resulting in an accident that could have been completely avoided. Have this code diagnosed and repaired immediately.
What repairs can fix the P0724 code?
The most common repair here is replacement of the brake light switch. Others include:
- Adjusting the brake light switch
- Repairing or replacing damaged wiring
- Replacing a blown fuse
- Replacing a failed torque converter lock-up solenoid
Additional comments for consideration regarding the P0724 code
Note that the Check Engine Light may or may not come on when the P0724 code is stored, depending on which system (PCM or ABS) noted the voltage abnormality.
Need help with a P0724 code?
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