AutoCodes – Buick – C0266 Buick

C0266 Buick Code - EBCM Motor Relay Circuit High When Off

Quick Answer

The ABS relay supplies battery voltage to six valve solenoids (RF dump/isolation, LF dump/isolation, and rear dump/isolation). Common causes include Faulty Electronic Brake Control Module (EBCM), Electronic Brake Control Module (EBCM) harness is open or shorted, Electronic Brake Control Module (EBCM) 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: C0266 Buick indicates EBCM Motor Relay Circuit High When Off.
Common causes: Common causes include Faulty Electronic Brake Control Module (EBCM), Electronic Brake Control Module (EBCM) harness is open or shorted, Electronic Brake Control Module (EBCM) 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 1,300

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 May 02, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code C0266 Buick Description

The ABS relay supplies battery voltage to six valve solenoids (RF dump/isolation, LF dump/isolation, and rear dump/isolation). The Electronic Brake Control Module (EBCM) microprocessor applies the grounds needed to activate each solenoid. The low side of each solenoid coil has a feedback circuit to the EBCM microprocessor. When a solenoid is commanded OFF, the feedback voltage is high. When a solenoid is commanded ON, the feedback voltage is low.

OBDII Code C0266 Buick - EBCM Motor Relay Circuit High When Off - AutoCodes.com — C0266 Buick Code - EBCM Motor Relay Circuit High When Off

What does this mean?

What are the Possible Causes of the DTC C0266 Buick?

Faulty Electronic Brake Control Module (EBCM)
Electronic Brake Control Module (EBCM) harness is open or shorted
Electronic Brake Control Module (EBCM) circuit poor electrical connection

How to Fix the DTC C0266 Buick?

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 C0266 Buick 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 C0266 Buick Code

1. What does the OBDII code C0266 mean on a Buick?

The C0266 code indicates an issue with the EBCM (Electronic Brake Control Module) motor relay circuit, specifically that it is reading "high" when it should be off.

2. What are the symptoms of the C0266 code in a Buick?

Common symptoms include the ABS warning light being illuminated, reduced or disabled ABS functionality, and potential braking system performance issues.

3. What causes the C0266 code to appear in a Buick?

The primary causes include a faulty EBCM, a damaged motor relay, corroded or loose electrical connections, or a short/open circuit in the wiring.

4. Is the C0266 code serious?

Yes, it can be serious as it affects the ABS system, which is critical for safe braking in certain conditions. Immediate diagnosis and repair are recommended.

5. How is the C0266 code diagnosed?

A technician will typically use a scan tool to confirm the code, inspect the EBCM motor relay circuit, check wiring and connections, and test the relay and EBCM for proper operation.

6. Can I drive my Buick with the C0266 code present?

While the vehicle may still be drivable, the ABS system may be compromised, increasing the risk of skidding or loss of control during hard braking or on slippery surfaces.

7. How do I fix the C0266 code on my Buick?

Repairs may involve replacing a faulty EBCM, repairing damaged wiring, cleaning corroded connections, or replacing the motor relay if it's defective.

8. How much does it cost to fix the C0266 code on a Buick?

The cost can vary depending on the issue, but EBCM replacement can range from $800 to $1,500, while wiring or relay repairs are generally less expensive.

9. Can a weak battery cause the C0266 code?

Yes, a weak or failing battery can contribute to electrical issues, potentially triggering this code. Ensure the battery and charging system are functioning properly.

10. How can I prevent the C0266 code from occurring again?

Regular maintenance, such as inspecting and cleaning electrical connections, checking for damaged wiring, and ensuring the ABS system is functioning correctly, can help prevent this code.