Damaged, chafed, or corroded wiring in the brake pressure sensor G circuit, especially near the sensor connector or where the harness flexes; Loose or contaminated electrical connector at the brake pressure sensor G; Failed brake pressure sensor G, reading low or open internally; Low brake fluid level or air in the hydraulic system causing abnormal pressure readings; Faulty electronic brake control module (EBCM) or ABS control module, though this is less common; Poor ground connection shared by the sensor or module, raising reference voltage errors; Aftermarket or incorrect sensor installed during prior brake work

DTC codes / C06xx · Brakes, steering and suspension / C0637

C0637Brake Pressure Sensor G Circuit Low

Q: What does code C0637 mean?

Brake Pressure Sensor G Circuit Low. C0637 means the electronic brake control module has detected a low voltage signal on the circuit for brake pressure sensor G, which is one of the pressure sensors used by the stability control system to monitor hydraulic brake pressure. The module compares the sensor's output against expected values and flags this code when the signal stays below the plausible minimum for a set period.

C0637 means the electronic brake control module has detected a low voltage signal on the circuit for brake pressure sensor G, which is one of the pressure sensors used by the stability control system to monitor hydraulic brake pressure. The module compares the sensor's output against expected values and flags this code when the signal stays below the plausible minimum for a set period.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

Anti-lock brake (ABS) warning light illuminated on the dashboard
Traction control or stability control (ESC) warning light on, often with the ABS light
Brake pedal feels normal in most cases, with no change in stopping power
Often no symptoms besides the warning light
Reduced or disabled ABS and stability control functions during low-traction situations
In some vehicles, a chime or message advising the brake system needs service

Common causes, most likely first

Damaged, chafed, or corroded wiring in the brake pressure sensor G circuit, especially near the sensor connector or where the harness flexes
Loose or contaminated electrical connector at the brake pressure sensor G
Failed brake pressure sensor G, reading low or open internally
Low brake fluid level or air in the hydraulic system causing abnormal pressure readings
Faulty electronic brake control module (EBCM) or ABS control module, though this is less common
Poor ground connection shared by the sensor or module, raising reference voltage errors
Aftermarket or incorrect sensor installed during prior brake work

How to diagnose and fix it

Check brake fluid level and inspect for visible leaks around the master cylinder and brake lines
Inspect the brake pressure sensor G connector and harness for corrosion, looseness, or chafing, and clean or repair as needed
Use a scan tool to read live brake pressure sensor G data and compare it to expected values with the pedal released and applied
Perform a voltage drop test on the sensor's power, ground, and signal wires to rule out high resistance
If wiring and connectors are good, test the sensor's resistance and output signal against the manufacturer's specification
Replace brake pressure sensor G if it fails electrical testing, then clear codes and verify the signal reads correctly
If the sensor and wiring test good, check for EBCM software updates or internal faults before condemning the module

What a low brake pressure signal really means

A low signal code does not automatically mean the sensor has failed; a poor ground or corroded connector can pull the signal voltage down and mimic a bad sensor.
Low brake fluid or trapped air can cause the sensor to read outside its expected range, so always verify the hydraulic system before replacing electrical parts.
Some vehicles use brake pressure sensor G as part of the hill-start assist or adaptive cruise control system, so a fault here can disable features beyond ABS.
After brake hydraulic repairs, air trapped near the pressure sensor can set this code until a proper bleed procedure is completed.
A failing EBCM can set a low signal code on multiple pressure sensors at once, which is a clue to look at the module rather than individual sensors.

Can I keep driving with C0637?

You can usually drive the vehicle with this code because normal braking remains functional, but ABS and stability control may be disabled. Avoid hard braking or emergency maneuvers at speed and have the fault diagnosed promptly, especially if the brake pedal feel changes.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.