AutoCodes – Generic – U2109

U2109 Code - Lost Communications With Powertrain Multiple Control System

Quick Answer

Modules connected to the Controller Area Network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Powertrain Multiple Control System, Powertrain Multiple Control System harness is open or shorted, Powertrain Multiple Control System 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: U2109 indicates Lost Communications With Powertrain Multiple Control System.
Common causes: Common causes include Faulty Powertrain Multiple Control System, Powertrain Multiple Control System harness is open or shorted, Powertrain Multiple Control System 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 3,706

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 Jun 15, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U2109 Description

Modules connected to the Controller Area Network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module. A module with a CAN serial data circuits malfunction or which loses power during the current ignition cycle will have a Loss of Communication Diagnostic Trouble Code (DTC) set by other modules that depend on information from that failed module. If any of the CAN circuit are shorted to battery voltage, ground, or between them no communication is possible on the CAN serial data bus, a Diagnostic Trouble Code will set.

OBDII Code U2109 - Lost Communications With Powertrain Multiple Control System - AutoCodes.com — U2109 Code - Lost Communications With Powertrain Multiple Control System

What does this mean?

What are the Possible Causes of the DTC U2109?

Faulty Powertrain Multiple Control System
Powertrain Multiple Control System harness is open or shorted
Powertrain Multiple Control System circuit poor electrical connection

How to Fix the DTC U2109?

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 U2109 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 U2109 code?

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Need Help with the Code?

Get the U2109 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U2109 Buick — Lost Communications With Powertrain Multiple Control System
U2109 Cadillac — Lost Communications With Powertrain Multiple Control System
U2109 Chevrolet — Lost Communications With Powertrain Multiple Control System
U2109 GMC — Lost Communications With Powertrain Multiple Control System

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 U2109 Code

1. What are the common symptoms of OBDII code U2109 "Lost Communications With Powertrain Multiple Control System"?

- Common symptoms include check engine light illuminating, difficulty shifting gears, and loss of power while driving.

2. What are the possible causes of OBDII code U2109?

- Possible causes include a faulty control module, damaged wiring or connectors, loose connections, or issues with the powertrain control module.

3. How can I diagnose the root cause of OBDII code U2109?

- Diagnosing the issue may require using a professional OBDII scanner to retrieve the specific fault codes, inspecting the wiring and connectors for damage or corrosion, and checking for loose connections.

4. Can I still drive my vehicle with OBDII code U2109 present?

- It is not recommended to continue driving the vehicle with this code present, as it can lead to further damage and potential safety hazards. It is best to address the issue promptly.

5. How can I reset OBDII code U2109?

- Resetting the code can be done using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes. However, it is important to address the underlying issue causing the code before resetting it.

6. Is OBDII code U2109 easy to repair?

- Repairing this code can vary in complexity depending on the underlying cause. It may range from simple fixes like tightening loose connections to more involved repairs like replacing a control module.

7. Can a DIY enthusiast fix OBDII code U2109 at home?

- While some aspects of diagnosing and repairing this code may be done at home by experienced DIY enthusiasts, certain repairs may require professional assistance, especially when dealing with control modules or complex wiring issues.

8. How much does it typically cost to repair OBDII code U2109?

- Repair costs can vary depending on the specific cause of the code, the extent of the issue, and whether professional labor is required. Costs may range from a few hundred to over a thousand dollars.

9. What are the potential risks of ignoring OBDII code U2109?

- Ignoring this code can lead to further damage to the powertrain control system, decreased fuel efficiency, and potential safety risks while driving. It is important to address the issue promptly.

10. How long does it take to repair OBDII code U2109?

- The repair time for this code can vary based on the complexity of the underlying issue and the availability of parts. It may range from a few hours to a full day or more, depending on the situation.