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Engine-Codes – GMC – U1555 GMC

U1555 GMC Code - Body Control Module Lost Communication With Left Rear Seat Heating/Venting/Cooling Switch On LIN Bus

Quick Answer

The U1555 GMC diagnostic trouble code indicates that the Body Control Module (BCM) has lost communication with the Left Rear Seat Heating/Venting/Cooling Switch on the Local Interconnect Network (LIN) Bus. Common causes include Faulty Left Rear Seat Heating/Venting/Cooling Switch, Wiring or connection issues in the LIN Bus network, BCM software glitch or malfunction. 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
U1555 GMC indicates Body Control Module Lost Communication With Left Rear Seat Heating/Venting/Cooling Switch On LIN Bus.
Common causes
Common causes include Faulty Left Rear Seat Heating/Venting/Cooling Switch, Wiring or connection issues in the LIN Bus network, BCM software glitch or malfunction.
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 12, 2024
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Code U1555 GMC Description

The U1555 GMC diagnostic trouble code indicates that the Body Control Module (BCM) has lost communication with the Left Rear Seat Heating/Venting/Cooling Switch on the Local Interconnect Network (LIN) Bus. The LIN Bus is a communication network used by various modules in the vehicle to exchange data and control signals. In this case, the BCM is unable to communicate with the switch responsible for controlling the left rear seat's heating, venting, or cooling functions.

OBDII Code U1555 GMC - Body Control Module Lost Communication With Left Rear Seat Heating/Venting/Cooling Switch On LIN Bus
U1555 GMC Code - Body Control Module Lost Communication With Left Rear Seat Heating/Venting/Cooling Switch On LIN Bus

Common Causes of U1555 GMC

  1. Faulty Left Rear Seat Heating/Venting/Cooling Switch
  2. Wiring or connection issues in the LIN Bus network
  3. BCM software glitch or malfunction
  4. Water or moisture intrusion affecting the electrical components
  5. Physical damage to the BCM or switch due to impact or wear

Symptoms of U1555 GMC

  1. Inoperative left rear seat heating/cooling functions
  2. Error message on the instrument cluster related to the left rear seat controls
  3. Malfunctioning climate control system in the rear of the vehicle
  4. BCM-related warning lights illuminated on the dashboard

How to Fix U1555 GMC

  1. Begin by conducting a thorough inspection of the wiring harness and connectors associated with the left rear seat switch and the BCM. Look for any signs of damage, corrosion, or loose connections.
  2. Use a diagnostic scan tool to communicate with the BCM and retrieve specific fault codes related to the U1555 issue. This will help pinpoint the exact source of the communication failure.
  3. Test the functionality of the Left Rear Seat Heating/Venting/Cooling Switch to determine if it is operating correctly. Replace the switch if necessary.
  4. If no issues are found with the switch, proceed to check the LIN Bus network for any faults. Repair or replace any damaged wiring or connectors as needed.
  5. Clear the fault codes from the BCM's memory using the diagnostic tool and perform a final test to ensure that communication is restored between the BCM and the left rear seat switch.

Cost to Fix U1555 GMC

The typical repair costs for addressing the U1555 GMC code can vary depending on the specific cause of the issue. In general, replacing a faulty Left Rear Seat Heating/Venting/Cooling Switch can cost between $100 and $200, including parts and labor. If the problem lies in the wiring or BCM, the repair costs may increase due to the additional diagnostic and labor time required.

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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 U1555 GMC Code

1. What are common symptoms of OBDII code U1555 in a GMC vehicle?

- Common symptoms include malfunctioning left rear seat heating, venting, or cooling system, loss of communication with the body control module, and potential warning lights on the dashboard.

2. What causes the OBDII code U1555 GMC - Body Control Module Lost Communication With Left Rear Seat Heating/Venting/Cooling Switch On LIN Bus?

- This code is typically triggered by a communication error between the body control module and the left rear seat heating/cooling switch on the LIN bus network.

3. How can I diagnose the issue related to code U1555 GMC?

- Diagnosis usually involves checking the wiring connections between the body control module and the left rear seat heating/cooling switch, as well as testing the components for proper functionality.

4. Is it safe to continue driving with the U1555 fault code?

- While the vehicle may still be operable, it is recommended to address the issue promptly to ensure the proper functioning of the left rear seat heating/cooling system and prevent any potential electrical problems.

5. How can the U1555 GMC code be repaired?

- Repairing the U1555 code often involves inspecting and repairing any damaged wiring, ensuring proper connections, and potentially replacing the left rear seat heating/cooling switch if necessary.

6. Can a DIY enthusiast fix the U1555 code issue?

- Depending on the individual's skill level and access to tools, some DIY enthusiasts may be able to address the U1555 code by following diagnostic procedures and making necessary repairs to the wiring or components.

7. Is it necessary to reset the OBDII code U1555 after repairs are made?

- Yes, it is recommended to reset the code after repairs to clear the fault memory in the system and ensure the issue has been successfully resolved.

8. Are there any common related codes that may accompany U1555 in a GMC vehicle?

- Other related codes that may accompany U1555 include communication faults with other modules or switches in the LIN bus network, such as U1554 or U1556.

9. How can I prevent the recurrence of the U1555 code in the future?

- Regularly inspecting and maintaining the wiring and components related to the left rear seat heating/cooling system can help prevent the recurrence of the U1555 code in the future.

10. Should I seek professional help for repairing the U1555 GMC code?

- If you are unsure about diagnosing or repairing the U1555 code, it is advisable to seek professional help from a qualified mechanic or dealership to ensure the issue is properly addressed.

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