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Engine-Codes – Generic – U1255

U1255 Code - Lost Communications

Quick Answer

The U1255 diagnostic trouble code (DTC) refers to "Lost Communications" within the vehicle's network system. Common causes include Faulty Wiring: Damaged or frayed wiring harnesses can disrupt communication between modules, Corroded Connectors: Corrosion on connectors can interfere with the flow of data signals, Defective Modules: A malfunctioning ECU or control module can cause communication failures. 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
U1255 indicates Lost Communications.
Common causes
Common causes include Faulty Wiring: Damaged or frayed wiring harnesses can disrupt communication between modules, Corroded Connectors: Corrosion on connectors can interfere with the flow of data signals, Defective Modules: A malfunctioning ECU or control module can cause communication failures.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 06, 2024
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Code U1255 Description

The U1255 diagnostic trouble code (DTC) refers to "Lost Communications" within the vehicle's network system. This code indicates a failure in the communication between different modules or systems within the vehicle. Modern vehicles are equipped with numerous electronic control units (ECUs) that communicate with each other through a network system known as Controller Area Network (CAN). When the communication between these modules is interrupted or lost, the U1255 code is triggered.

OBDII Code U1255 - Lost Communications
U1255 Code - Lost Communications

Common Causes of U1255

  1. Faulty Wiring: Damaged or frayed wiring harnesses can disrupt communication between modules.
  2. Corroded Connectors: Corrosion on connectors can interfere with the flow of data signals.
  3. Defective Modules: A malfunctioning ECU or control module can cause communication failures.
  4. CAN Bus Issues: Problems with the CAN bus itself, such as a short circuit or network overload, can trigger the U1255 code.
  5. Water Intrusion: Water intrusion into the vehicle's electrical system can lead to communication issues between modules.

Symptoms of U1255

  1. Check Engine Light: The most common symptom associated with the U1255 code is the illumination of the check engine light on the dashboard.
  2. Erratic Behavior: The vehicle may exhibit erratic behavior, such as stalling, rough idling, or sudden loss of power.
  3. Inoperative Systems: Various systems in the vehicle, such as ABS, airbags, or traction control, may become inoperative.
  4. Poor Fuel Efficiency: A loss of communication between modules can lead to poor fuel efficiency due to suboptimal engine performance.
  5. Transmission Issues: Communication failures can also result in transmission issues, such as delayed shifting or harsh gear changes.

How to Fix U1255

  1. Diagnose the Issue: Use a professional diagnostic scan tool to identify which modules are not communicating properly.
  2. Inspect Wiring and Connectors: Check for any damaged wiring or corroded connectors and repair or replace them as needed.
  3. Test Modules: Test the functionality of each module to determine if any are defective and require replacement.
  4. Repair CAN Bus: If issues are found with the CAN bus, repair or replace the affected components to restore proper communication.
  5. Clear Codes: After making the necessary repairs, clear the U1255 code from the vehicle's system using a scan tool.

Cost to Fix U1255

The typical cost to repair a U1255 code can vary depending on the specific cause of the communication failure and the extent of the repairs needed. In general, the cost of parts and labor for addressing this issue can range from $200 to $500. However, it's important to note that diagnosis time and labor rates at auto repair shops can vary significantly. Rates can range from $80 to $150 per hour, with higher rates in metropolitan areas or at dealerships, and lower rates at independent shops. It's advisable to consult with a trusted mechanic to get a more accurate estimate based on your vehicle's make and model.

What does this mean?

Tech Notes for U1255

The code is set when the Powertrain Control Module (PCM) does not receive a message that it was expecting from another control module (e.g. Transmission Control Module, ABS Module), and does not know which control module did not send the message.

As with all loss of communication concerns, inspect the power, ground, and serial data circuits to the suspect module prior to replacing any parts.

When is the Code Detected?

U1255 is set when the control module does not receive a message that it was expecting from another control module, and does not know which control module did not send that message.

Need more information about the U1255 code?

Need more information on how to fix the U1255 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1255 code diagnosed by a professional: Find a repair shop in your area

Code U1255 Information for Specific Makes

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 U1255 Code

1. What does the OBDII code U1255 mean?

U1255 indicates a loss of communication between modules on the vehicle's communication network, often related to the Controller Area Network (CAN) bus.

2. What are the common symptoms of code U1255?

Symptoms may include warning lights on the dashboard, erratic or inoperative gauges, failure of certain electronic systems, or intermittent loss of functionality.

3. What causes the U1255 code to appear?

Common causes include a faulty module, damaged wiring, a loose or corroded connector, or a failing communication bus.

4. Can a low battery cause the U1255 code?

Yes, a low or weak battery can disrupt module communication and trigger the U1255 code.

5. How do I diagnose code U1255?

Start by checking the battery voltage, inspecting wiring and connectors for damage, and verifying continuity in the communication network using a scan tool.

6. Can I drive with the U1255 code?

It depends on the affected systems. While some systems may remain operational, critical safety or performance-related features could be compromised.

7. What modules are typically affected by the U1255 code?

Any module on the communication bus can be involved, such as the ECM, TCM, ABS module, or BCM, depending on the vehicle.

8. How do I fix the U1255 code?

Repairs may include cleaning or securing connectors, repairing damaged wiring, replacing a faulty module, or reprogramming a module if necessary.

9. Is special equipment needed to troubleshoot the U1255 code?

Yes, a scan tool capable of reading manufacturer-specific data and analyzing the communication network is often required.

10. Can the U1255 code clear itself?

If the issue is intermittent, the code may clear temporarily, but the underlying problem must be addressed to prevent recurrence.

Discuss the causes and fixes for U1255 OBDII Code

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