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The transmission takes the power produced by the engine and sends that force to the drive wheels. An automatic transmission handles the tiring job of engaging and disengaging the clutches with the appropriate gear sets whenever the driver changes gear.

The powertrain control module (PCM) controls every facet of the automatic transmission’s operation, including which clutch to use and when to engage it. If the PCM notices clutch slippage during shifting, it will log a P0811 code.

What Does the P0811 Code Mean?

The diagnostic trouble code (DTC) P0811 indicates “Excessive Clutch ‘A’ Slippage.” It applies to OBD-II-compliant vehicles with multi-speed automatic transmission.

Most multispeed automatic transmissions have several planetary gear sets. Each set enables a specific gear ratio that gets the most output from the engine within a certain operating range.

stepping on clutch pedal
When the PCM notices clutch slippage during shifting, it will log a P0811 code.

The transmission manages these planetary gear sets with control devices like bands and clutches. It switches between gears by disengaging the previously used clutch from its gear set while engaging the new clutch and gear set together.

The transmission relies on hydraulic fluid to activate its clutches and engage its gear sets. A pump that draws power from the engine puts the fluid under pressure and moves the medium through the valve body. The pressurized fluid flows through the valve leading to the clutch that will engage the best gear for the job.

The PCM regularly checks the input speed sensor and output speed sensors. If their readings show clutch slippage in the transmission, the controller will set the generic powertrain code P0811.

Note: The definition of code P0811 can differ according to the vehicle manufacturer. Check the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0811 Code?

  • Internal transmission failure
  • Low or dirty fluid
  • Valve body problems
  • An issue with the PCM, such as software in need of an update

What are the Common Symptoms of P0811 Code?

automotive valve body image
Valve body problems can trigger the code P0811.

How to Diagnose the P0811 Code

The P0811 code is a generic powertrain code that can be logged by various makes and models. Depending on various factors, its root cause and symptoms can vary between vehicles. That means there’s no single solution to every instance of this trouble code.

If you aren’t confident about conducting diagnostic tests on your vehicle, it’s a good idea to bring it to a professional mechanic. Otherwise, you can go ahead and diagnose the issue yourself.

How to Fix the P0811 Code

If you don’t have all the right tools and sufficient DIY auto repair experience, you’ll find it difficult to fix a P0811 code’s underlying issues. In most cases, it’s best to turn your vehicle over to professionals whom you trust.

DIYers with advanced technical knowledge and hands-on experience can test and replace their vehicle’s transmission. If you’re one of them, you should consult the appropriate repair manual or refer to an online repair database for additional information on the problem and the parts involved.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at CarParts.com

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

File Under : OBD-II Trouble Codes
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