What is an OBD2 code?

An OBD2 (On-Board Diagnostics) code is a diagnostic trouble code (DTC) generated by your vehicle's computer system when it detects a problem. These codes help identify specific issues with your vehicle's engine, transmission, emissions, or other systems.

How do I read OBD2 codes?

To read OBD2 codes, you'll need an OBD2 scanner. Plug it into your vehicle's OBD2 port (usually located under the dashboard), turn your key to the 'ON' position, and follow your scanner's instructions to retrieve the codes. Each code starts with a letter (P, B, C, or U) followed by four numbers.

What do the different types of OBD2 codes mean?

OBD2 codes are categorized by their first letter: P (Powertrain) for engine and transmission issues, B (Body) for interior systems like airbags, C (Chassis) for mechanical systems like brakes, and U (Network) for computer and module communication problems.

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Home » OBD2 Codes » C0637

Code C0637

Symptoms

• ABS warning light is on

• Brake system warning light is on

• Reduced braking performance

Common Causes

• Faulty brake pressure sensor

• Damaged wiring or connectors

• Malfunctioning ABS module

Glossary

ABS: Anti-lock Braking System

OBD-II: On-Board Diagnostics II

Related Codes

• C0638

• C0639

Laymans terms

This means that the car's computer is getting a weak signal from a sensor that helps measure how hard you're pressing the brake pedal.

Explanation

The brake pressure sensor measures the pressure applied to the brakes. A 'circuit low' code indicates that the sensor is sending a signal that is lower than expected.

Technical description

The C0637 code is triggered when the brake pressure sensor G circuit is reading a voltage level that is lower than the manufacturer's specified range. This could be due to a malfunctioning sensor, wiring issues, or a problem with the vehicle's computer.

Diagnosis steps

• Use an OBD-II scanner to confirm the code.

• Inspect the brake pressure sensor and its wiring for damage.

• Test the sensor's voltage output with a multimeter.

Repair procedures

• Replace the brake pressure sensor if faulty.

• Repair or replace damaged wiring or connectors.

• Reprogram or replace the ABS module if necessary.

Tools required

• OBD-II scanner

• Multimeter

• Basic hand tools

Estimated repair cost

$100 - $300

Difficulty level

Moderate

Commonly affected vehicles

• Chevrolet Silverado

• GMC Sierra

• Cadillac Escalade

Preventive measures

• Regularly inspect brake system components.

• Ensure proper maintenance of ABS system.

• Check wiring and connectors for corrosion or damage.

Error code type

Sensor Issue

User experience recommendations

• Do not ignore the ABS warning light.

• Get the vehicle checked by a professional mechanic.

Warranty information

Check with your vehicle manufacturer for warranty coverage on brake system components.

Historical data

This code has been associated with brake pressure sensor issues in several vehicle models over the years.

Urgency level

Moderate – It is important to address this issue soon to ensure proper braking performance.

Legal and safety notice

Driving with a malfunctioning brake system can be dangerous. Address this issue promptly to ensure vehicle safety.

Testing conditions

• Engine running

• Vehicle stationary

Component location

The brake pressure sensor is typically located near the master cylinder or integrated into the ABS module.

FAQs

Q: Can I drive with a C0637 code?
A: It's not advisable to drive with this code as it can affect braking performance.

Q: How do I reset the ABS light?
A: Fix the underlying issue first, then use an OBD-II scanner to clear the code.

Last updated: Jun 8, 2026 • Source: internal database

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