AutoCodes – GMC – U0166 GMC

U0166 GMC Code - Lost Communication With Auxiliary Heater Control Module

Quick Answer

Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Auxiliary Heater Control Module, Auxiliary Heater Control Module harness is open or shorted, Auxiliary Heater Control Module 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: U0166 GMC indicates Lost Communication With Auxiliary Heater Control Module.
Common causes: Common causes include Faulty Auxiliary Heater Control Module, Auxiliary Heater Control Module harness is open or shorted, Auxiliary Heater Control Module 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 989

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 02, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0166 GMC Description

Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Auxiliary Heater Control Module has not been received.

OBDII Code U0166 GMC - Lost Communication With Auxiliary Heater Control Module - AutoCodes.com — U0166 GMC Code - Lost Communication With Auxiliary Heater Control Module

What does this mean?

What are the Possible Causes of the DTC U0166 GMC?

Faulty Auxiliary Heater Control Module
Auxiliary Heater Control Module harness is open or shorted
Auxiliary Heater Control Module circuit poor electrical connection

How to Fix the DTC U0166 GMC?

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 U0166 GMC 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 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.