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U0140 2017 Toyota RAV4 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 2017 Toyota RAV4 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 190

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 2017 Toyota RAV4 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 2017 Toyota RAV4 - Lost Communication with Main Body ECU - AutoCodes.com — U0140 2017 Toyota RAV4 Code - Lost Communication with Main Body ECU

What does this mean?

What are the Possible Causes of the DTC U0140 2017 Toyota RAV4?

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 2017 Toyota RAV4?

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 2017 Toyota RAV4 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 2017 Toyota RAV4 Code

1. What does the OBDII code U0140 mean on a 2017 Toyota RAV4?

The code U0140 indicates a "Lost Communication with Main Body ECU" error in the vehicle's onboard diagnostics system.

2. What are the common symptoms of a U0140 code in a 2017 Toyota RAV4?

Common symptoms include issues with various electronic components such as power windows, door locks, lights, and climate control systems. The vehicle may also experience starting problems or dashboard warning lights.

3. What are the potential causes of a U0140 code in a 2017 Toyota RAV4?

Possible causes of the U0140 code include damaged wiring or connectors, faulty Main Body ECU, software issues, or a weak battery.

4. How can I diagnose a U0140 code in my 2017 Toyota RAV4?

Diagnosing the U0140 code typically involves using a diagnostic scanner to retrieve the specific details of the communication loss and inspecting the wiring, connectors, and ECU for any visible damage.

5. Can I still drive my 2017 Toyota RAV4 with a U0140 code?

It is not recommended to drive the vehicle with a U0140 code as it can lead to further electrical issues and potential safety hazards. It's best to address the problem promptly.

6. How can I repair a U0140 code in my 2017 Toyota RAV4?

Repairing a U0140 code may involve fixing or replacing damaged wiring or connectors, repairing or replacing the Main Body ECU, updating software, or addressing any underlying battery issues.

7. Is it possible to reset a U0140 code in a 2017 Toyota RAV4?

Resetting the code without addressing the root cause will not solve the underlying issue. It's crucial to diagnose and repair the problem causing the U0140 code before attempting to reset it.

8. Will a U0140 code in a 2017 Toyota RAV4 cause the vehicle to fail an emissions test?

Yes, a U0140 code can cause your vehicle to fail an emissions test since it indicates a communication problem with a critical electronic control unit.

9. How much does it typically cost to repair a U0140 code in a 2017 Toyota RAV4?

The cost of repairing a U0140 code can vary depending on the specific cause of the issue. It's advisable to consult a professional mechanic for an accurate diagnosis and cost estimate.

10. Can a U0140 code in a 2017 Toyota RAV4 be prevented?

Preventing a U0140 code involves regular maintenance, such as checking and maintaining the vehicle's electrical components, ensuring proper battery health, and addressing any warning signs promptly to prevent communication issues with the Main Body ECU.