AutoCodes – GMC – C128B 2018 GMC Sierra

C128B 2018 GMC Sierra Code - ABS Master Cylinder Pressure Sensor Offset Error

Quick Answer

The Electronic Brake Control Module uses inputs from the Electronic Brake Control Brake Pedal Position Sensor to determine when the brake is applied and how much force is used. Common causes include Faulty Electronic Brake Control Module (EBCM), Electronic Brake Control Module harness is open or shorted, Electronic Brake Control Module circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: C128B 2018 GMC Sierra indicates ABS Master Cylinder Pressure Sensor Offset Error.
Common causes: Common causes include Faulty Electronic Brake Control Module (EBCM), Electronic Brake Control Module harness is open or shorted, Electronic Brake Control Module circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 207

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 13, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code C128B 2018 GMC Sierra Description

The Electronic Brake Control Module uses inputs from the Electronic Brake Control Brake Pedal Position Sensor to determine when the brake is applied and how much force is used. The Electronic Brake Control Module monitors when the driver's foot is on the brake and locks the offset. The offset is locked when three out of the four inputs indicate the brake pedal is applied. The four inputs are brake pedal travel 1, brake pedal travel 2, master cylinder pressure sensor, and brake pedal position sensor. These inputs are used to determine the driver's braking intent which is used to control the amount of pressure applied to the wheels.
Brake pressure sensor information is communicated from the Electronic Brake Control Module (EBCM) to the Hybrid Control Processor (HCP). This information is used to schedule regenerative braking and engine autostops.
The Diagnostic Trouble Code (DTC) will be set when the Engine Control Module (ECM) detects a corrupted data message from the Electronic Brake Control Module.

OBDII Code C128B 2018 GMC Sierra - ABS Master Cylinder Pressure Sensor Offset Error - AutoCodes.com — C128B 2018 GMC Sierra Code - ABS Master Cylinder Pressure Sensor Offset Error

What does this mean?

What are the Possible Causes of the DTC C128B 2018 GMC Sierra?

Faulty Electronic Brake Control Module (EBCM)
Electronic Brake Control Module harness is open or shorted
Electronic Brake Control Module circuit poor electrical connection
Faulty Starter/Generator Control Module

How to Fix the DTC C128B 2018 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the C128B 2018 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the C128B 2018 GMC Sierra code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about C128B 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code C128B on a 2018 GMC Sierra?

The common symptoms of OBDII code C128B on a 2018 GMC Sierra include the ABS warning light illuminating on the dashboard, potential loss of ABS functionality, and decreased brake performance.

2. What does the OBDII code C128B indicate in a 2018 GMC Sierra?

OBDII code C128B for a 2018 GMC Sierra indicates an ABS Master Cylinder Pressure Sensor Offset Error. This means there is a discrepancy in the pressure sensor readings in the ABS system.

3. What are the possible causes of OBDII code C128B on a 2018 GMC Sierra?

Possible causes of OBDII code C128B on a 2018 GMC Sierra include a faulty ABS master cylinder pressure sensor, wiring issues, sensor calibration problems, or ABS module malfunctions.

4. How can I diagnose the ABS Master Cylinder Pressure Sensor Offset Error on my 2018 GMC Sierra?

Diagnosing the ABS Master Cylinder Pressure Sensor Offset Error on a 2018 GMC Sierra involves using an OBDII scanner to retrieve the specific code, checking the wiring and connections to the pressure sensor, and inspecting the sensor itself for any visible damage.

5. Can I still drive my 2018 GMC Sierra with OBDII code C128B present?

While it is possible to drive with OBDII code C128B on a 2018 GMC Sierra, it is not recommended due to potential issues with ABS functionality and brake performance. It's advisable to address the problem promptly.

6. How can I repair OBDII code C128B on my 2018 GMC Sierra?

Repairing OBDII code C128B on a 2018 GMC Sierra may involve replacing the ABS master cylinder pressure sensor, repairing any damaged wiring, recalibrating the sensor, or addressing any underlying ABS module issues.

7. Is resetting the OBDII code C128B on a 2018 GMC Sierra enough to fix the problem?

Simply resetting the OBDII code C128B on a 2018 GMC Sierra may temporarily clear the warning light, but it will not fix the underlying issue causing the ABS Master Cylinder Pressure Sensor Offset Error.

8. Can a DIY enthusiast fix OBDII code C128B on a 2018 GMC Sierra?

While some aspects of diagnosing and repairing OBDII code C128B on a 2018 GMC Sierra may be tackled by a knowledgeable DIY enthusiast, it is advisable to seek professional assistance due to the complexity of ABS systems.

9. How much does it cost to repair OBDII code C128B on a 2018 GMC Sierra?

The cost to repair OBDII code C128B on a 2018 GMC Sierra can vary depending on the specific cause of the issue, labor rates, and parts needed. It's recommended to obtain quotes from reputable mechanics or dealerships.

10. Can unresolved OBDII code C128B cause further damage to a 2018 GMC Sierra?

Leaving OBDII code C128B unresolved on a 2018 GMC Sierra can potentially lead to further damage to the ABS system, compromised brake safety, and overall reduced vehicle performance. Addressing the issue promptly is crucial.