AutoCodes – Lexus – U0140 Lexus

U0140 Lexus Code - Lost Communication with Main Body ECU

Quick Answer

The Controller Area Network (CAN) is a standard bus system in vehicles that enables the connection of automotive devices without the need for a host computer. Common causes include Faulty Controller Area Network (CAN) Communication System, Faulty Main Body ECU, Main Body ECU harness is open or shorted. 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: U0140 Lexus indicates Lost Communication with Main Body ECU.
Common causes: Common causes include Faulty Controller Area Network (CAN) Communication System, Faulty Main Body ECU, Main Body ECU harness is open or shorted.
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 803

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 26, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U0140 Lexus Description

The Controller Area Network (CAN) is a standard bus system in vehicles that enables the connection of automotive devices without the need for a host computer. The exchange of operating information and commands among devices is facilitated by pre-programmed information about the required message exchange on the serial data circuits. Communication is carried out using two dedicated wires, known as CAN high and CAN low, with both lines carrying 2.5V when the CAN bus is in idle mode. During the transmission of data bits, the CAN high line increases to 3.75V while the CAN low drops to 1.25V, creating 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 Main Body ECU has not been received.

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OBDII Code U0140 Lexus - Lost Communication with Main Body ECU - AutoCodes.com — U0140 Lexus Code - Lost Communication with Main Body ECU

What does this mean?

What are the Possible Causes of the DTC U0140 Lexus?

Faulty Controller Area Network (CAN) Communication System
Faulty Main Body ECU
Main Body ECU harness is open or shorted
Main Body ECU circuit poor electrical connection

How to Fix the DTC U0140 Lexus?

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 does this mean?

Code Tech Notes

When there are problems with the way different systems in a vehicle communicate with each other using a technology called Controller Area Network (CAN) communication, Diagnostic Trouble Codes (DTC) are displayed. These codes can be caused by issues with the main bus or branch of the communication network, or with the Electronic Control Units (ECUs) and sensors that make up the different systems. If you see code for both the CAN communication problems and internal or power source problems at the same time, you should focus on fixing the internal or power source problems first.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0140 Lexus 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 U0140 Lexus Code

1. What are common symptoms of the OBDII code U0140 in a Lexus indicating "Lost Communication with Main Body ECU"?

Common symptoms include dashboard warning lights illuminating, loss of certain vehicle functions like power windows or door locks, and intermittent or complete loss of communication with the main body ECU.

2. What are some possible causes of the U0140 code in a Lexus?

Possible causes include a faulty main body ECU, damaged wiring or connectors leading to the main body ECU, a weak or dead vehicle battery, or software issues within the ECU.

3. How can I diagnose the U0140 code in my Lexus?

Diagnosing the U0140 code typically involves using a diagnostic scanner to retrieve the code, checking for related codes, inspecting wiring and connectors for damage, and testing the main body ECU and related components for proper function.

4. Can I continue driving my Lexus with the U0140 code present?

It is not recommended to drive your Lexus with the U0140 code present as it may lead to further electrical issues or safety concerns due to loss of communication with the main body ECU.

5. How can I repair the U0140 code in my Lexus?

Repairing the U0140 code may involve replacing the main body ECU, repairing damaged wiring or connectors, ensuring the vehicle battery is in good condition, and performing any necessary software updates.

6. Are there any DIY tips for resolving the U0140 code in a Lexus?

DIY tips include checking and securing wiring connections, ensuring the vehicle battery is properly charged, and clearing the code with a diagnostic scanner to see if it returns after repairs.

7. Is the U0140 code common in Lexus vehicles?

The U0140 code "Lost Communication with Main Body ECU" can occur in Lexus vehicles, especially in older models or vehicles with high mileage, due to potential wear and tear on electrical components.

8. Can a mechanic help me fix the U0140 code in my Lexus?

Yes, a qualified mechanic with experience in diagnosing and repairing electronic control unit issues can assist in fixing the U0140 code in your Lexus.

9. How much does it typically cost to repair the U0140 code in a Lexus?

The cost of repairing the U0140 code can vary depending on the specific cause and extent of the issue, but it may range from a few hundred to over a thousand dollars for parts and labor.

10. Will resetting the U0140 code make it go away permanently?

Simply resetting the U0140 code may not make it go away permanently if the underlying issue, such as a faulty main body ECU or damaged wiring, is not addressed. It's important to diagnose and repair the root cause of the code for a lasting solution.