AutoCodes – Generic – U0166

U0166 Code - Lost Communication With Auxiliary Heater Control Module

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. 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 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 12,629

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 Description

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines. Since communication relies on a voltage differential between the two bus lines, the CAN bus is NOT sensitive to inductive spikes, electrical fields, or other noise. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Auxiliary Heater Control Module has not been received.

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

What does this mean?

What are the Possible Causes of the DTC U0166?

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?

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 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.

Need more information about the U0166 code?

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Need Help with the Code?

Get the U0166 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U0166 Buick — Lost Communication With Auxiliary Heater Control Module
U0166 Cadillac — Lost Communication With Auxiliary Heater Control Module
U0166 Chevrolet — Lost Communication With Auxiliary Heater Control Module
U0166 GMC — Lost Communication With Auxiliary Heater Control Module

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 Code

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

- Common symptoms include loss of control over the auxiliary heater, failure of the heater to operate, and an illuminated check engine light.

2. What can cause OBDII code U0166 to appear?

- Possible causes include a faulty auxiliary heater control module, damaged wiring or connectors, a blown fuse, or a communication error within the vehicle's network.

3. How can I diagnose the issue related to code U0166?

- Use a diagnostic scanner to retrieve the code, inspect the wiring and connectors for any visible damage, and perform a thorough check of the auxiliary heater control module.

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

- It is not recommended to drive with this code, as it may result in a malfunctioning auxiliary heater, which is important for maintaining comfort and visibility in colder weather.

5. Can I repair OBDII code U0166 on my own?

- Depending on your automotive knowledge and skills, you may be able to address this issue by checking and repairing any damaged wiring or connectors associated with the auxiliary heater control module.

6. How much does it typically cost to fix OBDII code U0166?

- The cost of repairing this code can vary based on the specific cause of the issue. It may involve simple repairs like fixing wiring or require replacement of the auxiliary heater control module.

7. Are there any preventive measures to avoid OBDII code U0166 from appearing?

- Regularly inspecting the auxiliary heater control system and ensuring proper maintenance can help prevent issues that lead to the communication loss with the control module.

8. Can a low battery voltage trigger OBDII code U0166?

- Yes, a low battery voltage or electrical system issues can sometimes lead to communication errors with the auxiliary heater control module, resulting in the appearance of code U0166.

9. Will resetting the OBDII system clear code U0166?

- Resetting the OBDII system may temporarily clear the code, but if the underlying issue is not addressed, the code is likely to reappear once the communication error with the auxiliary heater control module persists.

10. How urgent is it to address OBDII code U0166?

- While the vehicle may still be operable with this code present, it is important to address it in a timely manner to ensure the proper functioning of the auxiliary heater system and prevent any potential safety hazards or discomfort during colder weather.