AutoCodes – Chevrolet – U1866 Chevrolet

U1866 Chevrolet 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 Chevrolet 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 705

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

What does this mean?

What are the Possible Causes of the DTC U1866 Chevrolet?

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 Chevrolet?

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 Chevrolet 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 Chevrolet Code

1. What does the OBDII code U1866 mean on a Chevrolet?

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

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

Symptoms may include warning lights on the dashboard, erratic electrical issues, failure to start, or reduced hybrid/electric performance if applicable.

3. What causes the U1866 code to appear on a Chevrolet?

Common causes include faulty wiring or connectors between the modules, a malfunctioning BECM or BCM, or software issues within the modules.

4. Can a weak battery cause the U1866 code on a Chevrolet?

Yes, a weak or failing 12V battery can lead to communication errors and trigger the U1866 code.

5. How do I diagnose the U1866 code on a Chevrolet?

Diagnosis involves inspecting the wiring and connectors between the BECM and BCM, checking for power and ground to the modules, and scanning for additional codes.

6. Can the U1866 code be fixed without replacing parts?

Yes, the issue can sometimes be resolved by repairing damaged wiring, cleaning corroded connectors, or updating module software.

7. Is it safe to drive a Chevrolet with the U1866 code?

Driving may be unsafe as the code can affect vehicle performance or critical functions, especially in hybrid or electric models.

8. How much does it cost to repair the U1866 code on a Chevrolet?

Repair costs can vary widely, from under $100 for minor wiring fixes to $500 or more if a module replacement is needed.

9. Can clearing the U1866 code with a scan tool fix the problem?

Clearing the code may temporarily turn off the warning, but the underlying issue must be resolved to prevent the code from returning.

10. Do I need a professional to fix the U1866 code on a Chevrolet?

While minor wiring issues can be addressed by experienced DIYers, diagnosing and repairing module-related problems often requires a professional with specialized tools.