AutoCodes – Generic – U1011

U1011 Code - CAN Communication Bus - Signal Malfunction

Quick Answer

The Controller Area Network (CAN) is a serial communication line for real-time applications. Common causes include Controller Area Network (CAN) communication harness is open or shorted, Faulty Engine Control Module (ECM), Poor harness ground 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: U1011 indicates CAN Communication Bus - Signal Malfunction.
Common causes: Common causes include Controller Area Network (CAN) communication harness is open or shorted, Faulty Engine Control Module (ECM), Poor harness ground 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 21,269

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 16, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code U1011 Description

The Controller Area Network (CAN) is a serial communication line for real-time applications. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads the required data only.
The Diagnostic Trouble Code (DTC) sets when detecting errors during the initial diagnosis of CAN controller of the Engine Control Module (ECM).

OBDII Code U1011 - CAN Communication Bus - Signal Malfunction - AutoCodes.com — U1011 Code - CAN Communication Bus - Signal Malfunction

What does this mean?

What are the Possible Causes of the DTC U1011?

Controller Area Network (CAN) communication harness is open or shorted
Faulty Engine Control Module (ECM)
Poor harness ground connection.

How to Fix the DTC U1011?

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 U1011 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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Information for Specific Makes

U1011 Ford — Invalid Internal Control Module Monitoring Data Received From ECM/PCM
U1011 Lincoln — Invalid Internal Control Module Monitoring Data Received From ECM/PCM
U1011 Mercury — Invalid Internal Control Module Monitoring Data Received From ECM/PCM
U1011 Nissan — CAN Communication Bus - Signal Malfunction

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.