AutoCodes – Mercedes-Benz – P0766 Mercedes-Benz

P0766 Mercedes-Benz Code - Shift Solenoid 'D' Performance or Stuck Off

Quick Answer

Shift solenoid valve 'D' is turned ON or OFF by the Transmission Control Module (TCM) in response to signals sent from the park/neutral position (PNP) switch, vehicle speed and Engine Control Module (ECM) (throttle opening). Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty shift solenoid 'D' valve. 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: P0766 Mercedes-Benz indicates Shift Solenoid 'D' Performance or Stuck Off.
Common causes: Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty shift solenoid 'D' valve.
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 4,670

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0766 Mercedes-Benz Description

OBDII Code P0766 Mercedes-Benz - Shift Solenoid 'D' Performance or Stuck Off - AutoCodes.com — P0766 Mercedes-Benz Code - Shift Solenoid 'D' Performance or Stuck Off

What does this mean?

What are the Possible Causes of the DTC P0766 Mercedes-Benz?

Low transmission fluid level
Dirty transmission fluid
Faulty shift solenoid 'D' valve
Shift solenoid 'D' valve harness or connectors
Shift solenoid 'D' valve circuit is open or shorted

How to Fix the DTC P0766 Mercedes-Benz?

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 does this mean?

Code Tech Notes

When the a transmission solenoid is stuck off, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is very dirty, it is recommend changing the transmission fluid and if possible removing the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a transmission mechanical failure and that the transmission will need to be rebuilt or replaced.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0766 Mercedes-Benz 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 P0766 Mercedes-Benz code?

Need more information on how to fix the P0766 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 P0766 Mercedes-Benz Code

1. What does the OBDII code P0766 mean on a Mercedes-Benz?

P0766 indicates a problem with the Shift Solenoid 'D' in the transmission, either due to a performance issue or the solenoid being stuck in the "off" position.

2. What are the common symptoms of code P0766 in a Mercedes-Benz?

Symptoms may include erratic shifting, failure to shift to certain gears, transmission slipping, poor fuel economy, or the vehicle entering limp mode.

3. What causes the P0766 code in a Mercedes-Benz?

Common causes include a faulty shift solenoid, dirty or low transmission fluid, wiring or connector issues, or internal transmission damage.

4. Can low transmission fluid cause the P0766 code?

Yes, low or dirty transmission fluid can lead to improper solenoid operation and trigger the P0766 code.

5. How do you diagnose the P0766 code in a Mercedes-Benz?

Diagnosis typically involves scanning the vehicle with an OBDII tool, inspecting transmission fluid levels, checking the solenoid's electrical connections, and testing the solenoid's functionality.

6. Can I drive my Mercedes-Benz with a P0766 code?

Driving with a P0766 code is not recommended, as it may cause further damage to the transmission and lead to unsafe driving conditions.

7. How is the P0766 code repaired on a Mercedes-Benz?

Repairs may include replacing the faulty shift solenoid, cleaning or refilling the transmission fluid, repairing damaged wiring, or rebuilding the transmission if internal damage is found.

8. How much does it cost to fix a P0766 code in a Mercedes-Benz?

Repair costs can vary widely, ranging from $150-$400 for solenoid replacement to $2,000 or more for transmission repairs, depending on the severity of the issue.

9. Can a software update fix the P0766 code in a Mercedes-Benz?

In rare cases, a transmission control module (TCM) software update may resolve the issue, but this is only applicable if a known software glitch is causing the problem.

10. How can I prevent the P0766 code from occurring in my Mercedes-Benz?

Regularly check and maintain proper transmission fluid levels, avoid aggressive driving, and perform routine transmission service as recommended by the manufacturer.