AutoCodes – Saturn – U0121 Saturn

U0121 Saturn Code - Lost Communication With Electronic Brake Control Module

Quick Answer

Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Electronic Brake Control Module (EBCM), EBCM harness is open or shorted, 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: U0121 Saturn indicates Lost Communication With Electronic Brake Control Module.
Common causes: Common causes include Faulty Electronic Brake Control Module (EBCM), EBCM harness is open or shorted, 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 11,785

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 Mar 30, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0121 Saturn Description

Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Electronic Brake Control Module (EBCM) has not been received.

OBDII Code U0121 Saturn - Lost Communication With Electronic Brake Control Module - AutoCodes.com — U0121 Saturn Code - Lost Communication With Electronic Brake Control Module

What does this mean?

What are the Possible Causes of the DTC U0121 Saturn?

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

How to Fix the DTC U0121 Saturn?

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 U0121 Saturn 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 U0121 Saturn code?

Need more information on how to fix the U0121 Saturn code? Get Access to Factory Service Manuals

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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 U0121 Saturn Code

1. What are the common symptoms of OBDII code U0121 in a Saturn related to lost communication with the Electronic Brake Control Module (EBCM)?

The common symptoms include the ABS warning light illuminating on the dashboard, loss of ABS functionality, traction control issues, and potential difficulty in shifting gears.

2. What are the possible causes of the U0121 code in a Saturn indicating a communication problem with the EBCM?

The code U0121 can be triggered by issues such as a faulty EBCM, damaged wiring or connectors leading to the EBCM, corrosion in the electrical connections, or a malfunctioning CAN bus system.

3. How can I diagnose the U0121 code in my Saturn to pinpoint the exact cause of the communication failure with the EBCM?

Diagnosing the U0121 code typically involves using a diagnostic scan tool to retrieve the trouble codes, checking the wiring and connectors for any visible damage, testing the EBCM and related components, and performing a thorough inspection of the CAN bus network.

4. Is it safe to drive my Saturn with the U0121 code indicating a lost communication with the EBCM?

It is not recommended to drive your Saturn with the U0121 code present, as it indicates a potential problem with the electronic brake control system, which could compromise the vehicle's braking performance and safety features.

5. How can I reset the U0121 code in my Saturn after repairing the issue with the EBCM communication?

Once you have fixed the underlying issue causing the U0121 code, you can reset the code using a diagnostic scan tool or by disconnecting the car's battery for a few minutes to clear the error codes.

6. Are there any DIY repair tips for addressing the U0121 code related to lost communication with the EBCM in a Saturn?

While diagnosing and repairing the U0121 code may require advanced automotive knowledge and specialized tools, basic DIY steps include checking for loose or damaged connections, cleaning corroded terminals, and ensuring proper grounding of the EBCM.

7. Can a malfunctioning wheel speed sensor cause the U0121 code to appear in a Saturn?

Yes, a malfunctioning wheel speed sensor can disrupt communication with the EBCM and trigger the U0121 code. It is recommended to inspect and test all wheel speed sensors if this code is present.

8. How much does it typically cost to repair the U0121 code in a Saturn caused by lost communication with the EBCM?

The cost of repairing the U0121 code can vary depending on the exact cause of the communication failure. It may range from a few hundred to over a thousand dollars, including parts and labor.

9. Is the U0121 code common in Saturn vehicles, or is it a rare issue?

The U0121 code related to lost communication with the EBCM is not uncommon in Saturn vehicles, especially in models equipped with advanced brake control systems. It is a known issue that may require professional diagnosis and repair.

10. Can a software update or reprogramming of the EBCM resolve the U0121 code in a Saturn?

In some cases, updating the software or reprogramming the EBCM can help resolve communication issues and clear the U0121 code. It is recommended to consult a qualified mechanic or dealership for this procedure.