AutoCodes – Generic – U186A

U186A Code - Electronic Brake 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: U186A indicates Electronic Brake 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 1,722

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 U186A 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 U186A - Electronic Brake Control Module Lost Communication With Engine Control Module - AutoCodes.com — U186A Code - Electronic Brake Control Module Lost Communication With Engine Control Module

What does this mean?

What are the Possible Causes of the DTC U186A?

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 U186A?

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 U186A 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 U186A code?

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Need Help with the Code?

Get the U186A code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U186A Buick — Electronic Brake Control Module Lost Communication With Engine Control Module
U186A Cadillac — Electronic Brake Control Module Lost Communication With Engine Control Module
U186A Chevrolet — Electronic Brake Control Module Lost Communication With Engine Control Module
U186A GMC — Electronic Brake 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 U186A Code

1. What does the OBDII code U186A mean?

U186A indicates a communication failure between the Electronic Brake Control Module (EBCM) and the Engine Control Module (ECM).

2. What are the common symptoms of the U186A code?

Symptoms may include ABS or traction control warning lights, poor brake performance, engine performance issues, or a lack of communication with diagnostic tools.

3. What causes the U186A code to appear?

Common causes include damaged wiring or connectors, a faulty EBCM or ECM, software issues, or interference in the communication network.

4. Can a weak battery cause the U186A code?

Yes, a weak or failing battery may cause voltage drops that disrupt module communication, triggering the U186A code.

5. How do you diagnose the U186A code?

Diagnosis involves scanning for related codes, inspecting wiring and connectors for damage, testing the CAN bus network, and checking for proper power and ground at the modules.

6. Is it safe to drive with the U186A code?

Driving may be unsafe due to potential brake system malfunctions or reduced traction control, so the issue should be addressed promptly.

7. What repairs can fix the U186A code?

Repairs may include fixing or replacing damaged wiring or connectors, reprogramming or updating module software, or replacing a faulty EBCM or ECM.

8. How much does it cost to repair the U186A code?

Costs vary depending on the issue, but repairs typically range from $100 for wiring fixes to over $1,000 for module replacements.

9. Can a software update resolve the U186A code?

Yes, if the communication issue is caused by outdated module software, a reprogramming or update may resolve the problem.

10. What tools are needed to troubleshoot the U186A code?

Diagnostic tools like an advanced OBDII scanner with CAN bus analysis capabilities and a multimeter are typically required for troubleshooting.

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