AutoCodes – Toyota – U0140 Toyota

U0140 Toyota 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 Toyota 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 2,783

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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

What does this mean?

What are the Possible Causes of the DTC U0140 Toyota?

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 Toyota?

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 Toyota 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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Need Help with the Code?

Get the U0140 Toyota code diagnosed by a professional: Find a repair shop in your area

Information for Specific Toyota Models

U0140 2013 Toyota RAV4 — Lost Communication with Main Body ECU
U0140 2014 Toyota RAV4 — Lost Communication with Main Body ECU
U0140 2015 Toyota RAV4 — Lost Communication with Main Body ECU
U0140 2016 Toyota RAV4 — Lost Communication with Main Body ECU
U0140 2017 Toyota RAV4 — Lost Communication with Main Body ECU
U0140 2018 Toyota RAV4 — Lost Communication with Main Body ECU

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 Toyota Code

1. What are the common symptoms of OBDII code U0140 in a Toyota indicating a lost communication with the Main Body ECU?

- Common symptoms may include issues with interior lights, power windows, door locks, or other features controlled by the Main Body ECU.

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

- The U0140 code can be triggered by a faulty Main Body ECU, damaged wiring or connectors, low battery voltage, or a communication network issue.

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

- Diagnose the U0140 code by checking the wiring and connectors for any damage, testing the battery voltage, and performing a scan tool communication check with the Main Body ECU.

4. Can I drive my Toyota with the U0140 code present?

- It is not recommended to drive your Toyota with the U0140 code present, as it can lead to unreliable operation of various vehicle systems controlled by the Main Body ECU.

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

- Repair options include repairing or replacing damaged wiring, connectors, or the Main Body ECU, ensuring proper battery voltage, and addressing any communication network issues.

6. Is it necessary to reset the U0140 code after repairing the issue in my Toyota?

- Yes, it is recommended to clear the U0140 code after repairing the issue to reset the vehicle's system and ensure proper operation.

7. Can a DIY enthusiast fix the U0140 code issue in a Toyota?

- DIY enthusiasts may be able to diagnose and fix simple causes of the U0140 code, such as checking wiring and connectors, but more complex issues may require professional assistance.

8. How long does it typically take to repair the U0140 code in a Toyota?

- The repair time for the U0140 code can vary depending on the exact cause of the issue, ranging from a few hours for simple fixes to longer for more complicated repairs.

9. Are there any preventive measures to avoid the U0140 code in a Toyota?

- Regular maintenance checks, avoiding electrical system overloads, and ensuring proper battery health can help prevent issues leading to the U0140 code.

10. Can the U0140 code in a Toyota cause other problems if left unresolved?

- Yes, leaving the U0140 code unresolved can lead to further electrical system malfunctions, affecting the overall performance and safety of your Toyota.