Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with the electric motor that helps you brake. It's not getting enough power to work properly.
The code indicates that the current in the brake booster motor's U-V-W phases is lower than expected, which can affect the brake system's performance.
The brake booster motor assists in applying the brakes by providing additional force. The motor operates using three-phase electrical power (U, V, and W phases). A low current condition in these phases suggests an electrical issue, possibly due to a faulty motor or wiring problem.
• Reduced braking performance
• Brake warning light on the dashboard
• Unusual noises when braking
• Faulty brake booster motor
• Damaged or corroded wiring/connectors
• Faulty control module
Brake Booster: A device that increases the force applied to the brakes.
Current: The flow of electrical charge in a circuit.
• Inspect the brake booster motor and its wiring for damage.
• Check the electrical connections for corrosion or looseness.
• Test the motor's current draw using a multimeter.
• Replace the brake booster motor if faulty.
• Repair or replace damaged wiring or connectors.
• Replace the control module if necessary.
• Multimeter
• Wrench set
• Screwdriver set
$200 - $600
Moderate
• Chevrolet Malibu
• Buick LaCrosse
• Cadillac CTS
• Regularly inspect brake system components.
• Ensure electrical connections are secure and corrosion-free.
• Follow the manufacturer's maintenance schedule.
Brake System Issue
• Do not ignore the brake warning light.
• Have your vehicle inspected by a professional if you notice braking issues.
Check with your vehicle manufacturer for warranty coverage on brake system components.
This code commonly appears in vehicles with electric brake booster systems, particularly in models with high mileage.
High – Braking issues should be addressed immediately to ensure vehicle safety.
Driving with impaired brakes can lead to accidents and is illegal in many jurisdictions.
• Vehicle stationary
• Engine running
The brake booster motor is typically located near the brake master cylinder in the engine bay.
Q: Can I drive with code C0591?
A: It's not recommended to drive with this code as it indicates potential brake issues.
Q: How do I reset the brake warning light?
A: The warning light will reset after the issue is fixed. A diagnostic tool can also be used to clear the code.
Pro · Four-system diagnostics
A handheld scanner aimed at engine, transmission, ABS, and airbag diagnostic work.
Chassis and ABS faults usually need a scanner that can read brake-system data directly.
View on Amazon
Universal · Torque wrench
Useful when reassembly torque matters for wheel, suspension, and under-hood fasteners.
Useful when wheel, hub, or suspension hardware needs correct reassembly torque.
View on Amazon
Universal · Drive-on ramps
Helpful for safer access underneath the vehicle during exhaust, EVAP, and underbody inspection work.
Helpful for safer access during underbody inspection work.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.