Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that there's a problem with the sensor that checks how hard you're pressing the brake pedal. It's like when your game controller doesn't know how hard you're pressing the button.
The C0639 code indicates an issue with the brake pressure sensor circuit, specifically that it is open or has a fault.
The brake pressure sensor measures the pressure applied to the brake system and sends this information to the vehicle's computer. An 'H Circuit/Open' fault suggests that the sensor circuit is not completing, possibly due to a broken wire, disconnected connector, or a faulty sensor.
• ABS warning light on the dashboard
• Brake system warning light
• Reduced braking performance
• Faulty brake pressure sensor
• Damaged wiring or connectors in the brake pressure sensor circuit
• Faulty ABS control module
ABS: Anti-lock Braking System
OBD-II: On-Board Diagnostics, Second Generation
• Use an OBD-II scanner to confirm the C0639 code.
• Inspect the brake pressure sensor and its wiring for damage or disconnection.
• Test the brake pressure sensor using a multimeter to ensure it is functioning correctly.
• Replace the faulty brake pressure sensor.
• Repair or replace damaged wiring or connectors.
• Replace the ABS control module if found to be faulty.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $400
Moderate
• Chevrolet Silverado
• GMC Sierra
• Cadillac Escalade
• Regularly inspect brake system components.
• Ensure all electrical connections are secure.
• Perform routine maintenance checks.
Sensor Issue
• Do not ignore the ABS warning light.
• Have your vehicle inspected by a professional if the code appears.
Check with your vehicle manufacturer for warranty coverage on brake system components.
The C0639 code has been reported in vehicles with electronic brake systems, particularly in models with advanced ABS technology.
High – Brake system issues can affect vehicle safety and should be addressed promptly.
Ignoring brake system warnings can lead to decreased vehicle safety and potential legal liabilities in the event of an accident.
• Vehicle stationary with the engine running.
• Brake pedal pressed to simulate braking conditions.
The brake pressure sensor is typically located near the master cylinder or integrated within the ABS module.
Q: Can I drive with the C0639 code?
A: It's not recommended to drive with this code active, as it may affect your braking performance.
Q: How do I reset the C0639 code?
A: After repairs, use an OBD-II scanner to clear the code. If the issue persists, further diagnosis is needed.
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.
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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.
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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.
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