AutoCodes – Generic – U0421

U0421 Code - Invalid Data Received From Suspension Control Module 'A'

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 Suspension Control Module 'A', Suspension Control Module 'A' harness is open or shorted, Suspension Control Module 'A' 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: U0421 indicates Invalid Data Received From Suspension Control Module 'A'.
Common causes: Common causes include Faulty Suspension Control Module 'A', Suspension Control Module 'A' harness is open or shorted, Suspension Control Module 'A' 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 23,735

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 11, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code U0421 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. Some devices are constantly receiving information from other devices through serial data communication network. The invalid data Diagnostic Trouble Code (DTC) will be set when a receiving device detects a discrepancy in the information it receives from the Suspension Control Module 'A' causing its integrity to be questioned.

OBDII Code U0421 - Invalid Data Received From Suspension Control Module 'A' - AutoCodes.com — U0421 Code - Invalid Data Received From Suspension Control Module 'A'

What does this mean?

What are the Possible Causes of the DTC U0421?

Faulty Suspension Control Module 'A'
Suspension Control Module 'A' harness is open or shorted
Suspension Control Module 'A' circuit poor electrical connection

How to Fix the DTC U0421?

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 U0421 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 U0421 code?

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Information for Specific Makes

U0421 Buick — Invalid Data Received From Suspension Control Module
U0421 Cadillac — Invalid Data Received From Suspension Control Module
U0421 Chevrolet — Invalid Data Received From Suspension Control Module
U0421 GMC — Invalid Data Received From Suspension Control Module

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.