Torque Converter/Brake Switch B Circuit High
The transmission control module detects that the brake switch circuit B voltage is too high, similar to a stuck accelerator pedal sensor that won't drop to idle. This prevents the transmission from properly controlling torque converter lockup and gear shifts.
The ECM monitors brake switch B circuit voltage to control torque converter engagement during braking and shifting. The circuit should toggle between ground (brake applied) and high voltage (brake released). A sustained high voltage signal indicates an open circuit, short to power, or failed brake switch.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Brake Switch B Voltage | 0-0.5V (brake applied) or 4.5-5.0V (brake released) | Stuck above 2.0V when brake should be applied |
| Signal Toggle Time | Switches within 100ms of brake pedal input | No voltage change or slow response indicating circuit failure |
Code P0725 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0725 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.