Cruise Control/Brake Switch A Circuit Low
Your car's cruise control brake switch is sending a weak electrical signal to the engine computer, like a dimly lit warning light instead of a bright one. The ECU can't properly detect when you press the brake pedal, which disables cruise control as a safety measure.
The ECU monitors the voltage signal from the brake switch circuit, which should toggle between high (brake released) and low (brake pressed). When the voltage stays abnormally low or fails to reach the expected threshold, the ECU logs a fault. This protects against unintended cruise control operation when brakes are applied.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Brake Switch Signal Voltage | 4.5V - 5.0V (inactive); 0V - 0.5V (active) | Voltage stuck below 0.8V or unable to switch properly |
| Circuit Resistance | Less than 10 ohms when closed | Greater than 50 ohms indicating corrosion or loose connection |
Code P0573 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, P0573 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.