AutoCodes – Generic – U0251

U0251 Code - Lost Communication With Running Board Control Module 'B'

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Common causes include Faulty Running Board Control Module 'B', Running Board Control Module 'B' harness is open or shorted, Running Board 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: U0251 indicates Lost Communication With Running Board Control Module 'B'.
Common causes: Common causes include Faulty Running Board Control Module 'B', Running Board Control Module 'B' harness is open or shorted, Running Board 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 2,063

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 Apr 04, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0251 Description

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating 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 Running Board Control Module 'B' has not been received.

OBDII Code U0251 - Lost Communication With Running Board Control Module 'B' - AutoCodes.com — U0251 Code - Lost Communication With Running Board Control Module 'B'

What does this mean?

What are the Possible Causes of the DTC U0251?

Faulty Running Board Control Module 'B'
Running Board Control Module 'B' harness is open or shorted
Running Board Control Module 'B' circuit poor electrical connection

How to Fix the DTC U0251?

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 U0251 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 U0251 Code

What does the OBDII code U0251 mean?

The code U0251 indicates a loss of communication between the vehicleâ€™s main control module and the Running Board Control Module 'B'.

What are the common symptoms of code U0251?

Symptoms may include non-functioning or stuck running boards, warning lights on the dashboard, or reduced functionality of other related systems.

What causes code U0251 to be triggered?

Common causes include damaged wiring, loose or corroded electrical connections, a malfunctioning Running Board Control Module 'B', or issues with the vehicleâ€™s CAN bus network.

Can I still drive my vehicle with code U0251?

Yes, you can usually drive the vehicle, but the running boards may not function properly, and other electrical systems could potentially be affected.

How do I diagnose code U0251?

Start by inspecting the wiring and connections related to the Running Board Control Module 'B'. Use a diagnostic scan tool to check for other related codes and test the CAN bus network.

What tools are needed to troubleshoot code U0251?

Youâ€™ll need a diagnostic scan tool with CAN bus functionality, a multimeter to test electrical circuits, and possibly wiring diagrams for your vehicle.

How can I repair code U0251?

Repairs may involve fixing or replacing damaged wiring, cleaning corroded connectors, updating module software, or replacing the Running Board Control Module 'B' if itâ€™s faulty.

Can a dead battery cause code U0251?

Yes, a weak or dead battery can disrupt communication between modules, potentially triggering U0251.

Do I need to replace the Running Board Control Module 'B' for code U0251?

Not always; the issue may be related to wiring or connections. Replace the module only after confirming itâ€™s faulty through proper diagnosis.

How much does it cost to fix code U0251?

Repair costs vary depending on the issue. Wiring repairs may cost $100-$300, while replacing the Running Board Control Module 'B' can cost $500-$1,000 or more.