AutoCodes – GMC – C0638 GMC

C0638 GMC Code - Left Front Normal Force Circuit High

Quick Answer

The Continuously Variable Road Sensing Suspension (CVRSS) module estimates the road surface and communicates that information to the Electronic Brake Control module (EBCM). Common causes include Faulty Electronic Brake Control module (EBCM), Electronic Brake Control module (EBCM) harness is open or shorted, Electronic Brake Control module (EBCM) 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: C0638 GMC indicates Left Front Normal Force Circuit High.
Common causes: Common causes include Faulty Electronic Brake Control module (EBCM), Electronic Brake Control module (EBCM) harness is open or shorted, Electronic Brake Control module (EBCM) 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 767

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 30, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code C0638 GMC Description

The Continuously Variable Road Sensing Suspension (CVRSS) module estimates the road surface and communicates that information to the Electronic Brake Control module (EBCM). The CVRSS module provides a Pulse Width Modulation (PWM) signal to the EBCM through the left and right normal force signal circuits. The CVRSS module sends each normal force value twice to the EBCM. The possible values of the PWM duty cycle are 20%, 40%, 60% and 80%, with the valid range from 10-90%. The EBCM uses this information to provide improved rough-road braking performance.

OBDII Code C0638 GMC - Left Front Normal Force Circuit High - AutoCodes.com — C0638 GMC Code - Left Front Normal Force Circuit High

What does this mean?

What are the Possible Causes of the DTC C0638 GMC?

Faulty Electronic Brake Control module (EBCM)
Electronic Brake Control module (EBCM) harness is open or shorted
Electronic Brake Control module (EBCM) circuit poor electrical connection

How to Fix the DTC C0638 GMC?

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 C0638 GMC 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 C0638 GMC code?

Need more information on how to fix the C0638 GMC code? Get Access to Factory Service Manuals

Need Help with the 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 C0638 GMC Code

1. What are some common symptoms of OBDII code C0638 GMC (Left Front Normal Force Circuit High)?

- Some common symptoms include the Service Stability message on the dashboard, traction control issues, and possible ABS system malfunctions.

2. What could be causing the OBDII code C0638 GMC to trigger?

- The code C0638 GMC is typically triggered by a faulty left front wheel speed sensor, damaged wiring, or a problem with the Electronic Brake Control Module (EBCM).

3. How can I diagnose the source of the OBDII code C0638 GMC?

- A thorough diagnosis involves checking the left front wheel speed sensor for proper operation, inspecting the wiring for any damage or loose connections, and performing a scan tool test on the EBCM.

4. Can I continue driving my vehicle with the OBDII code C0638 GMC present?

- It is not recommended to drive the vehicle with the C0638 code active, as it can affect the stability and control of the vehicle, especially in adverse driving conditions.

5. What are some repair tips for fixing the OBDII code C0638 GMC issue?

- Repairing the C0638 code may involve replacing the left front wheel speed sensor, repairing any damaged wiring, or reprogramming the EBCM if necessary.

6. Is it possible to reset the OBDII code C0638 GMC without fixing the underlying issue?

- Resetting the code without addressing the root cause will only temporarily clear the error code. The issue will likely reappear until the underlying problem is resolved.

7. How much can I expect to pay for repairs related to the OBDII code C0638 GMC?

- The cost of repairs for the C0638 code can vary depending on the specific issue, but it may range from a few hundred to a few thousand dollars, including parts and labor.

8. Will the OBDII code C0638 GMC affect my vehicle's overall performance?

- Yes, the C0638 code can impact your vehicle's stability and control systems, potentially affecting overall performance and safety while driving.

9. Can a DIY enthusiast fix the OBDII code C0638 GMC issue at home?

- Depending on the skill level and tools available, some DIY enthusiasts may be able to address the C0638 code by replacing the wheel speed sensor or repairing wiring. However, advanced diagnostics may require professional assistance.

10. How urgent is it to address the OBDII code C0638 GMC once it appears?

- It is recommended to address the C0638 code as soon as possible to prevent potential safety hazards and further damage to the vehicle's systems.