AutoCodes – Buick – U1866 Buick

U1866 Buick Code - Battery Energy Control Module Lost Communication With Body Control Module

Quick Answer

Modules connected to the Controller Area Network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Body Control Module (BCM), Body Control Module harness is open or shorted, Body 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: U1866 Buick indicates Battery Energy Control Module Lost Communication With Body Control Module.
Common causes: Common causes include Faulty Body Control Module (BCM), Body Control Module harness is open or shorted, Body 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 476

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 Jun 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1866 Buick Description

Modules connected to the Controller Area Network (CAN) 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. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module. A module with a CAN serial data circuits malfunction or which loses power during the current ignition cycle will have a Loss of Communication Diagnostic Trouble Code (DTC) set by other modules that depend on information from that failed module. If any of the CAN circuit are shorted to battery voltage, ground, or between them no communication is possible on the CAN serial data bus, a Diagnostic Trouble Code will set.

OBDII Code U1866 Buick - Battery Energy Control Module Lost Communication With Body Control Module - AutoCodes.com — U1866 Buick Code - Battery Energy Control Module Lost Communication With Body Control Module

What does this mean?

What are the Possible Causes of the DTC U1866 Buick?

Faulty Body Control Module (BCM)
Body Control Module harness is open or shorted
Body Control Module circuit poor electrical connection

How to Fix the DTC U1866 Buick?

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 U1866 Buick 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 U1866 Buick Code

1. What does OBDII code U1866 mean for a Buick?

U1866 indicates that the Battery Energy Control Module (BECM) has lost communication with the Body Control Module (BCM).

2. What are the common symptoms of U1866 on a Buick?

Symptoms may include warning lights on the dashboard, issues with hybrid or electric system performance, or failure of certain electrical components.

3. What causes the U1866 code to appear?

Common causes include damaged wiring or connectors, a malfunctioning BECM or BCM, software glitches, or electrical interference.

4. Can a weak battery trigger the U1866 code?

Yes, a weak or failing battery can cause communication issues between modules, potentially triggering the U1866 code.

5. How do you diagnose the U1866 code?

Diagnosis typically involves inspecting wiring and connectors, checking for module power and ground, and using a scan tool to monitor module communication.

6. Can I still drive my Buick with a U1866 code?

Driving with this code may be possible but is not recommended, as it could affect critical systems like the hybrid battery or electrical components.

7. How is the U1866 code fixed?

Repairs may involve replacing or repairing damaged wires or connectors, reprogramming one or both modules, or replacing a faulty module.

8. What tools are needed to troubleshoot the U1866 code?

You'll need an advanced scan tool with bi-directional control, a multimeter, and possibly an oscilloscope for in-depth diagnostics.

9. How much does it typically cost to repair a U1866 code?

Repair costs can vary widely, ranging from $100 for minor wiring fixes to over $1,000 if a module replacement is needed.

10. Can a software update resolve the U1866 code on a Buick?

Yes, if the issue is caused by a software glitch, a BCM or BECM software update performed by a dealership may resolve the problem.

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