AutoCodes – Infiniti – U0121 Infiniti

U0121 Infiniti Code - Lost Communication With Anti-Lock Brake System Control Module

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Common causes include Faulty Anti-Lock Brake System (ABS) Control Module, Anti-Lock Brake System Control Module harness is open or shorted, Anti-Lock Brake System 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: U0121 Infiniti indicates Lost Communication With Anti-Lock Brake System Control Module .
Common causes: Common causes include Faulty Anti-Lock Brake System (ABS) Control Module, Anti-Lock Brake System Control Module harness is open or shorted, Anti-Lock Brake System 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 1,322

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 Apr 06, 2020

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

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines. Since communication relies on a voltage differential between the two bus lines, the CAN bus is NOT sensitive to inductive spikes, electrical fields, or other noise. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Anti-Lock Brake System (ABS) Control Module has not been received.

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OBDII Code U0121 Infiniti - Lost Communication With Anti-Lock Brake System Control Module - AutoCodes.com — U0121 Infiniti Code - Lost Communication With Anti-Lock Brake System Control Module

What does this mean?

What are the Possible Causes of the DTC U0121 Infiniti?

Faulty Anti-Lock Brake System (ABS) Control Module
Anti-Lock Brake System Control Module harness is open or shorted
Anti-Lock Brake System Control Module circuit poor electrical connection

How to Fix the DTC U0121 Infiniti?

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 Infiniti 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.

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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 Infiniti Code

What does the OBDII code U0121 mean for my Infiniti?

U0121 indicates that there is a lost communication with the Anti-Lock Brake System (ABS) control module, which affects the vehicle's ability to monitor and control the ABS.

What are the common symptoms of a U0121 code?

Common symptoms include warning lights on the dashboard, such as the ABS light or traction control light, as well as potential issues with braking performance or stability control.

What could cause the U0121 code in my Infiniti?

Causes can include a faulty ABS control module, damaged wiring or connectors, issues with the vehicle's communication network, or problems with the engine control unit (ECU).

How can I diagnose the U0121 code?

To diagnose U0121, use an OBD-II scanner to confirm the code and check for additional codes. Inspect the wiring and connectors related to the ABS module for damage, corrosion, or loose connections.

Can I drive my Infiniti with the U0121 code?

It is not recommended to drive your vehicle with this code, as it may affect the performance of the braking system and could compromise safety.

What are some common repair tips for fixing the U0121 code?

Common repairs include checking and repairing any damaged wiring or connectors, replacing the ABS control module if faulty, and ensuring that all related electronic systems are functioning properly.

Is it necessary to reset the code after repairs?

Yes, after completing the repairs, it is important to clear the code using an OBD-II scanner and test drive the vehicle to ensure the issue is resolved.

Can a dead battery cause the U0121 code?

Yes, a dead or weak battery can lead to communication issues between modules, potentially triggering the U0121 code.

How much does it typically cost to repair the U0121 code?

Repair costs can vary widely depending on the exact cause, but expect to spend anywhere from $100 to $1,000, especially if the ABS control module needs to be replaced.