Cruise Control/Brake Switch A Circuit High
The cruise control brake switch circuit is stuck in a high voltage state, like a light switch that's permanently flipped on instead of toggling. The ECU expects this signal to toggle between high and low when you press the brake, but it's not doing that.
The ECU monitors the brake switch circuit voltage to detect when the brake pedal is pressed. The circuit should toggle between low voltage (brake pressed) and high voltage (brake released). When the voltage remains stuck high, the ECU cannot properly detect brake application and disables cruise control for safety.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Brake Switch Voltage | 0.5V (pressed) to 4.5V (released), toggling on pedal input | Constant 4.5V+ with no toggling or response to brake pedal |
| Circuit Response Time | Voltage change within 100ms of pedal press | No voltage change detected or delayed response |
Code P0574 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, P0574 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.