AutoCodes – GMC – U1861 GMC

U1861 GMC Code - Battery Charger Control Module Lost Communication With Engine 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 Engine Control Module (ECM), Engine Control Module harness is open or shorted, Engine 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: U1861 GMC indicates Battery Charger Control Module Lost Communication With Engine Control Module.
Common causes: Common causes include Faulty Engine Control Module (ECM), Engine Control Module harness is open or shorted, Engine 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 436

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 U1861 GMC 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 U1861 GMC - Battery Charger Control Module Lost Communication With Engine Control Module - AutoCodes.com — U1861 GMC Code - Battery Charger Control Module Lost Communication With Engine Control Module

What does this mean?

What are the Possible Causes of the DTC U1861 GMC?

Faulty Engine Control Module (ECM)
Engine Control Module harness is open or shorted
Engine Control Module circuit poor electrical connection

How to Fix the DTC U1861 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 U1861 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 U1861 GMC Code

What does the OBDII code U1861 mean for a GMC vehicle?

The code U1861 indicates a lost communication between the Battery Charger Control Module (BCCM) and the Engine Control Module (ECM).

What are the common symptoms of the U1861 code on a GMC?

Symptoms may include warning lights on the dashboard, failure to charge the battery properly, or reduced performance of electrical systems.

What causes the U1861 code to appear?

Common causes include faulty wiring or connections, a malfunctioning Battery Charger Control Module, a defective Engine Control Module, or issues with the vehicle’s CAN communication network.

Can a weak battery trigger the U1861 code on a GMC vehicle?

Yes, a weak or failing battery can disrupt communication between modules and potentially trigger this code.

How can I fix the U1861 code on my GMC?

Repairs may include inspecting and repairing wiring or connectors, replacing the Battery Charger Control Module or Engine Control Module if defective, and ensuring the battery and charging system are functioning correctly.

Is it safe to drive a GMC with the U1861 code active?

Driving may be possible, but it is not recommended as electrical system performance may be compromised, and the battery may not charge properly.

How can I diagnose the U1861 code on a GMC vehicle?

Use a diagnostic scanner to confirm the code, inspect wiring and connectors between the modules, and test the functionality of the Battery Charger Control Module and Engine Control Module.

Can a software issue cause the U1861 code on a GMC?

Yes, outdated or corrupted software in either the Battery Charger Control Module or Engine Control Module can lead to communication errors.

What tools are needed to troubleshoot the U1861 code on a GMC?

A diagnostic scanner, digital multimeter, and wiring diagrams are typically required for troubleshooting this code.

Does the U1861 code affect battery life in GMC vehicles?

Yes, if the Battery Charger Control Module cannot communicate with the Engine Control Module, the battery may not charge properly, leading to premature battery failure.