AutoCodes – Cadillac – U1866 Cadillac

U1866 Cadillac 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 Cadillac 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 594

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

What does this mean?

What are the Possible Causes of the DTC U1866 Cadillac?

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 Cadillac?

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 Cadillac 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 Cadillac Code

What does the OBDII code U1866 indicate for my Cadillac?

The U1866 code indicates that the Battery Energy Control Module (BECM) has lost communication with the Body Control Module (BCM), which can affect various electrical systems in your vehicle.

What are the common symptoms of the U1866 code?

Common symptoms include warning lights on the dashboard, problems with power accessories (like windows and locks), and issues with the vehicleâ€™s charging system.

What could cause the U1866 code to trigger?

Causes may include faulty wiring or connectors between the BECM and BCM, a malfunctioning BCM, or a dead battery affecting communication.

How can I diagnose the issue related to the U1866 code?

Start by checking the battery voltage and connections. Then, inspect the wiring and connectors between the BECM and BCM for damage or corrosion. Use a scan tool to check for additional codes that might provide more context.

Can I drive my Cadillac with the U1866 code?

While you may be able to drive, itâ€™s not advisable as the loss of communication can lead to further electrical issues, which could affect vehicle safety and performance.

What repairs may be needed to fix the U1866 code?

Repairs may involve fixing or replacing damaged wiring or connectors, replacing the BCM, or in some cases, replacing the BECM.

Is it possible to reset the U1866 code after repairs?

Yes, after addressing the underlying issue, you can clear the code using an OBDII scanner. However, itâ€™s essential to ensure the problem is resolved before resetting.

How much might it cost to repair the U1866 code?

Repair costs can vary widely depending on the specific issue. Basic wiring repairs might be relatively inexpensive, while replacing a BCM could cost several hundred dollars.

Can I prevent the U1866 code from occurring?

Regular vehicle maintenance, including battery checks and electrical system inspections, can help prevent issues that may lead to the U1866 code.