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Engine-Codes – GMC – U0166 GMC

U0166 GMC Code - Lost Communication With Auxiliary Heater Control Module

Quick Answer

The U0166 GMC code indicates that the vehicle's onboard computer has lost communication with the Auxiliary Heater Control Module. Common causes include Wiring issues such as a short circuit or open circuit, Faulty Auxiliary Heater Control Module, Communication bus issues within the vehicle's computer system. 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
U0166 GMC indicates Lost Communication With Auxiliary Heater Control Module.
Common causes
Common causes include Wiring issues such as a short circuit or open circuit, Faulty Auxiliary Heater Control Module, Communication bus issues within the vehicle's computer system.
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 U0166 GMC Description

The U0166 GMC code indicates that the vehicle's onboard computer has lost communication with the Auxiliary Heater Control Module. This module is responsible for controlling the operation of the auxiliary heater in the vehicle, which is used to provide additional heat to the cabin during cold weather conditions. When communication is lost with this module, it can lead to issues with the auxiliary heater not functioning properly or at all.

OBDII Code U0166 GMC - Lost Communication With Auxiliary Heater Control Module
U0166 GMC Code - Lost Communication With Auxiliary Heater Control Module

Common Causes of U0166 GMC

  1. Wiring issues such as a short circuit or open circuit.
  2. Faulty Auxiliary Heater Control Module.
  3. Communication bus issues within the vehicle's computer system.
  4. Corrosion or damage to connectors related to the auxiliary heater system.

Symptoms of U0166 GMC

  1. Lack of heat coming from the auxiliary heater.
  2. Error message on the vehicle's dashboard related to the auxiliary heater system.
  3. Inconsistent or intermittent operation of the auxiliary heater.
  4. Reduced fuel efficiency due to increased workload on the main heating system.

How to Fix U0166 GMC

  1. Begin by conducting a visual inspection of the wiring and connectors related to the auxiliary heater system.
  2. Use a multimeter to test the continuity of the wiring and check for any shorts or open circuits.
  3. Test the Auxiliary Heater Control Module for proper functionality and replace if necessary.
  4. Check for any corrosion or damage to connectors and repair or replace as needed.
  5. Clear the diagnostic trouble codes from the vehicle's computer system and test the auxiliary heater system for proper operation.

Cost to Fix U0166 GMC

The typical repair costs for addressing a U0166 GMC code can vary depending on the specific cause of the issue. In general, the cost of parts such as a new Auxiliary Heater Control Module and any necessary wiring or connectors can range from $200 to $500. Labor costs at an auto repair shop can add an additional $100 to $300 to the total repair bill. It's important to note that these are rough estimates, and actual costs may vary based on factors such as location, vehicle make and model, and the extent of the repairs needed. It's recommended to obtain quotes from local auto repair shops for a more accurate cost estimate.

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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 U0166 GMC Code

1. What are the common symptoms of OBDII code U0166 GMC (Lost Communication With Auxiliary Heater Control Module)?

- Common symptoms include issues with the auxiliary heater system, such as the heater not functioning properly or not turning on at all.

2. What are the possible causes of OBDII code U0166 GMC?

- The code U0166 typically indicates a communication problem between the vehicle's main computer and the auxiliary heater control module. Causes may include wiring issues, a faulty control module, or a poor connection.

3. How can I diagnose OBDII code U0166 GMC?

- Diagnosing this code usually involves checking the wiring and connections between the main computer and the auxiliary heater control module, as well as testing the control module itself for proper functionality.

4. Can a DIYer repair OBDII code U0166 GMC at home?

- While some basic troubleshooting like checking connections and fuses can be done at home, diagnosing and repairing communication issues with the auxiliary heater control module may require specialized tools and expertise, so it's recommended to consult a professional mechanic.

5. Are there any quick tips for fixing OBDII code U0166 GMC?

- Quick tips include checking all related fuses, ensuring all connections are secure, and resetting the vehicle's computer by disconnecting the battery for a few minutes before reconnecting it.

6. Is it safe to continue driving with OBDII code U0166 GMC present?

- It is generally safe to drive with this code present, especially if the only symptom is related to the auxiliary heater system. However, it's important to address the issue promptly to ensure proper functioning of the heater.

7. How much does it typically cost to repair OBDII code U0166 GMC?

- Repair costs for this code can vary depending on the exact cause of the communication issue. It's best to get a diagnostic from a mechanic to determine the specific repair needed.

8. Can extreme weather conditions trigger OBDII code U0166 GMC?

- Extreme cold or hot weather conditions can potentially affect the performance of the auxiliary heater system, which may lead to the communication issue indicated by the U0166 code.

9. Will disconnecting the battery reset OBDII code U0166 GMC?

- Disconnecting the battery may temporarily clear the code, but if the underlying issue causing the communication problem is not addressed, the code is likely to return.

10. How long does it typically take to repair OBDII code U0166 GMC?

- The repair time for this code can vary depending on the exact cause and complexity of the issue. Simple fixes like reconnecting a loose wire may take a short time, while diagnosing a faulty control module could take longer.

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