AutoCodes – Dodge – P0866 Dodge

P0866 Dodge Code - TCM Communication Circuit High

Quick Answer

The Engine Control Module (ECM) monitors the Transmission Control Module (TCM). Common causes include Faulty Transmission Control Module (TCM), Transmission Control Module (TCM) harness is open or shorted, Transmission Control Module (TCM) 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: P0866 Dodge indicates TCM Communication Circuit High.
Common causes: Common causes include Faulty Transmission Control Module (TCM), Transmission Control Module (TCM) harness is open or shorted, Transmission Control Module (TCM) 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 4,179

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 11, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P0866 Dodge Description

The Engine Control Module (ECM) monitors the Transmission Control Module (TCM). The ECM sets the OBDII when there is a problem communicating with the TCM.

OBDII Code P0866 Dodge - TCM Communication Circuit High - AutoCodes.com — P0866 Dodge Code - TCM Communication Circuit High

What does this mean?

What are the Possible Causes of the DTC P0866 Dodge?

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

How to Fix the DTC P0866 Dodge?

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 P0866 Dodge 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 P0866 Dodge code?

Need more information on how to fix the P0866 Dodge code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0866 Dodge code diagnosed by a professional: Find a repair shop in your area

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.