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Engine-Codes – GMC – U1255 GMC

U1255 GMC Code - Lost Communications

Quick Answer

The U1255 GMC code indicates that there is a communication error between various modules in the vehicle's network. Common causes include Faulty wiring or poor electrical connections between modules, Corrosion or damage to the connectors or pins in the communication network, Failed control modules such as the ECM, TCM, or BCM. 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 GMC indicates Lost Communications.
Common causes
Common causes include Faulty wiring or poor electrical connections between modules, Corrosion or damage to the connectors or pins in the communication network, Failed control modules such as the ECM, TCM, or BCM.
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 22, 2024
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Code U1255 GMC Description

The U1255 GMC code indicates that there is a communication error between various modules in the vehicle's network. This can include the Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), or other control units. When these modules are unable to communicate properly, it can lead to a range of issues affecting the vehicle's performance and functionality.

OBDII Code U1255 GMC - Lost Communications
U1255 GMC Code - Lost Communications

Common Causes of U1255 GMC

  1. Faulty wiring or poor electrical connections between modules.
  2. Corrosion or damage to the connectors or pins in the communication network.
  3. Failed control modules such as the ECM, TCM, or BCM.
  4. Software glitches or programming errors within the modules.
  5. Water damage or exposure to moisture affecting the control units.

Symptoms of U1255 GMC

  1. Check Engine Light illuminated on the dashboard.
  2. Loss of power or reduced engine performance.
  3. Transmission shifting issues or erratic behavior.
  4. ABS warning light or other warning lights appearing on the instrument cluster.
  5. Inability to communicate with the vehicle's onboard diagnostic system using a scan tool.

How to Fix U1255 GMC

  1. Begin by performing a thorough inspection of the wiring harnesses and connectors for any signs of damage, corrosion, or loose connections.
  2. Use a diagnostic scan tool to retrieve and clear the U1255 code from the vehicle's memory.
  3. Test the communication network between the modules to identify any faulty components or areas of concern.
  4. Replace any damaged wiring, connectors, or control modules as needed to restore proper communication.
  5. Perform a final scan to ensure that the code has been successfully cleared and that the modules are communicating effectively.

Cost to Fix U1255 GMC

The typical repair costs for addressing a U1255 GMC code can vary depending on the specific cause of the communication error. In general, the parts and labor involved in diagnosing and repairing this issue can range from $200 to $500 or more. It's important to note that diagnostic time and labor rates at auto repair shops can vary significantly, so it's advisable to check with local providers for a more accurate estimate based on your location, vehicle make and model, and engine type.

What does this mean?

Tech Notes for U1255 GMC

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 GMC code?

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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.

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