AutoCodes – Generic – U0291

U0291 Code - Lost Communication With Gear Shift Control Module 'B'

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to connect automotive devices without a host computer. Common causes include Faulty Gear Shift Control Module 'B', Gear Shift Control Module 'B' harness is open or shorted, Gear Shift Control Module 'B' 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: U0291 indicates Lost Communication With Gear Shift Control Module 'B'.
Common causes: Common causes include Faulty Gear Shift Control Module 'B', Gear Shift Control Module 'B' harness is open or shorted, Gear Shift Control Module 'B' 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 9,893

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 Aug 26, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0291 Description

A Controller Area Network (CAN) is a vehicle bus standard designed to connect automotive devices without a host computer. Operating information and commands are exchanged among the devices, which are programmed to know which messages need to be exchanged over the serial data circuits. The CAN bus uses two dedicated wires for communication, known as CAN high and CAN low. In idle mode, both lines carry 2.5V. During data transmission, the CAN high line rises to 3.75V and the CAN low drops to 1.25V, creating a 2.5V differential between the lines. Since communication depends on this voltage differential, the CAN bus is not sensitive to inductive spikes, electrical fields, or other forms of noise. A Diagnostic Trouble Code (DTC) is set when a periodic message from the Gear Shift Control Module 'B' is not received.

OBDII Code U0291 - Lost Communication With Gear Shift Control Module 'B' - AutoCodes.com — U0291 Code - Lost Communication With Gear Shift Control Module 'B'

What does this mean?

What are the Possible Causes of the DTC U0291?

Faulty Gear Shift Control Module 'B'
Gear Shift Control Module 'B' harness is open or shorted
Gear Shift Control Module 'B' circuit poor electrical connection

How to Fix the DTC U0291?

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 U0291 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 U0291 code?

Need more information on how to fix the U0291 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0291 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U0291 Chrysler — Lost Communication With Gear Shift Control Module 'B'
U0291 Dodge — Lost Communication With Gear Shift Control Module 'B'
U0291 Fiat — Lost Communication With Gear Shift Control Module 'B'
U0291 Jeep — Lost Communication With Gear Shift Control Module 'B'
U0291 RAM — Lost Communication With Gear Shift Control Module 'B'

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 U0291 Code

1. What are the common symptoms of OBDII code U0291?

The common symptoms of OBDII code U0291 include issues with shifting gears, transmission problems, warning lights on the dashboard, and the vehicle going into a limp mode.

2. What could cause the OBDII code U0291 to appear?

The code U0291 "Lost Communication With Gear Shift Control Module 'B'" can be triggered by a faulty gear shift control module, damaged wiring or connectors, issues with the CAN bus communication system, or a software glitch.

3. How can I diagnose the OBDII code U0291?

Diagnosing the U0291 code typically involves using a professional OBDII scanner to read the code, checking for any other related codes, inspecting the gear shift control module and its connections, and testing the communication lines for any faults.

4. Can I continue driving with the OBDII code U0291 present?

It is not recommended to continue driving with the U0291 code present, as it can lead to potential transmission issues and safety concerns. It is best to have the vehicle diagnosed and repaired as soon as possible.

5. How can I repair the OBDII code U0291?

Repairing the U0291 code may involve replacing the gear shift control module, repairing or replacing damaged wiring or connectors, resetting the control module, or updating the software to resolve any communication issues.

6. Is it possible to reset the OBDII code U0291 without repairs?

Resetting the U0291 code without addressing the underlying issue may only provide a temporary solution. It is recommended to diagnose the problem first and then clear the code after making necessary repairs.

7. Can a DIY enthusiast fix the OBDII code U0291?

While some DIY enthusiasts may have the skills to address the U0291 code, it is a complex issue that may require specialized tools and knowledge. It is advisable to consult with a professional mechanic for proper diagnosis and repair.

8. How much does it cost to repair the OBDII code U0291?

The cost of repairing the U0291 code can vary depending on the root cause of the issue, the extent of the repairs needed, and the labor rates of the repair shop. It is recommended to obtain quotes from multiple mechanics for an accurate estimate.

9. Will the OBDII code U0291 cause my vehicle to fail an emissions test?

The U0291 code itself may not directly cause your vehicle to fail an emissions test, but it indicates a problem that should be resolved to ensure proper functioning of the vehicle's transmission system and overall emissions compliance.

10. How can I prevent the OBDII code U0291 from reoccurring?

To prevent the U0291 code from reoccurring, it is important to address the root cause of the issue thoroughly, perform regular maintenance on the transmission system, and address any related issues promptly to maintain the health of the vehicle's electronics.