What Does P0571 Mean?
The ECM has detected a malfunction in the cruise control brake switch 'A' circuit. This brake switch signal is critical for canceling cruise control when the driver presses the brake pedal. The ECM monitors this circuit to ensure cruise control disengages immediately upon braking. A circuit malfunction may prevent cruise cancel on braking or cause false cancel events.
Common Causes
35%
Faulty brake light switch (cruise control input) that is out of adjustment or has worn internal contacts
25%
Damaged or corroded wiring between the brake switch and ECM cruise control brake input
25%
Brake pedal switch pushrod or bumper pad worn or broken, preventing proper switch actuation
15%
ECM internal fault on the brake switch input circuit or software mismatch between brake switch signals
Diagnostic Steps
1
Step 1: Check brake light operation. Press the brake pedal and verify brake lights illuminate and extinguish properly. If brake lights stay on or do not illuminate, the brake switch is likely faulty or misadjusted.
2
Step 2: Monitor the cruise control brake switch 'A' input on ECM live data while pressing and releasing the brake pedal. The signal should transition cleanly between ON and OFF states with no delay or bouncing.
3
Step 3: Inspect the brake light switch at the top of the brake pedal arm. Check that the switch plunger contacts the brake pedal arm properly. Look for a broken or deteriorated bumper pad that normally holds the switch in the released position.
4
Step 4: Disconnect the brake switch connector and measure the switch continuity in both pressed and released positions. The switch should toggle between open and closed circuit with a clean transition.
5
Step 5: If the switch tests good, check the wiring from the brake switch to the ECM for opens, shorts, or high resistance. Many vehicles use two separate brake switch circuits (one for brake lights, one for cruise cancel); ensure the correct circuit is being tested.
Estimated Repair Cost
$20 - $150
Parts + labor, varies by vehicle and location
The ECM has detected a malfunction in the cruise control brake switch 'A' circuit. This brake switch signal is critical for canceling cruise control when the driver presses the brake pedal. The ECM monitors this circuit to ensure cruise control disengages immediately upon braking. A circuit malfunct...
The most common cause of P0571 (Cruise Control/Brake Switch A Circuit Malfunction) is: Faulty brake light switch (cruise control input) that is out of adjustment or has worn internal contacts
Typical repair costs for P0571 range from $20 to $150, depending on the vehicle, location, and whether you do it yourself or go to a shop.
If the brake switch signal is stuck in the released state, cruise control may not disengage when the driver brakes, requiring the driver to use the cancel button or turn off the ignition. This is a significant safety concern that should be addressed promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0571 to identify the root cause.
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Quick Info
Category
Powertrain
System
Cruise Control / Brake System Interface
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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