AutoCodes – Generic – U1861

U1861 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 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 1,002

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

What does this mean?

What are the Possible Causes of the DTC U1861?

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?

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 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 U1861 code?

Need more information on how to fix the U1861 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1861 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U1861 Buick — Battery Charger Control Module Lost Communication With Engine Control Module
U1861 Cadillac — Battery Charger Control Module Lost Communication With Engine Control Module
U1861 Chevrolet — Battery Charger Control Module Lost Communication With Engine Control Module
U1861 GMC — Battery Charger Control Module Lost Communication With Engine 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 U1861 Code

1. What does OBDII code U1861 mean?

U1861 indicates that the Battery Charger Control Module (BCCM) has lost communication with the Engine Control Module (ECM), which could affect the vehicle's charging system performance.

2. What are the common symptoms of code U1861?

Symptoms may include a charging system warning light, difficulty maintaining battery charge, reduced fuel efficiency in hybrid/electric vehicles, or intermittent electrical issues.

3. What causes the U1861 code to appear?

Common causes include faulty wiring or connections between the BCCM and ECM, a malfunctioning BCCM or ECM, or issues with the vehicle's CAN bus communication network.

4. Can a weak battery cause the U1861 code?

Yes, a weak or failing battery can interrupt communication between modules, potentially triggering this code.

5. How is the U1861 code diagnosed?

Technicians typically use a scan tool to check for additional codes, inspect the wiring and connectors for damage, and test the BCCM and ECM for proper operation.

6. Can I drive my car with the U1861 code?

While the vehicle may still be drivable, ignoring this code can lead to battery or charging system issues, potentially leaving you stranded.

7. How do I fix the U1861 code?

Repairs may include fixing damaged wiring, cleaning or reconnecting loose connectors, updating module software, or replacing a faulty BCCM or ECM.

8. How much does it cost to repair code U1861?

The repair cost varies depending on the issue but can range from $100 for simple wiring repairs to over $1,000 if a module replacement is required.

9. Can a software update resolve the U1861 code?

In some cases, a software update for the BCCM or ECM can fix communication issues, especially if the manufacturer has released updates to address known problems.

10. How can I prevent the U1861 code from recurring?

Regular maintenance, including inspecting wiring and connectors, ensuring the battery is in good condition, and addressing warning lights promptly, can help prevent this code.