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I have an 04 c320 and a code P0221, the car runs great when…

Customer Question
I have an 04...

I have an 04 c320 and a code P0221, the car runs great when cold but when it warms up the transition will jump to a higher gear when I slow down

Mechanic's Assistant: Just to clarify, what's the exact code? And have you tried to reset it?

The code is P0221

Mechanic's Assistant: Are you fixing your C320 yourself? What have you tried so far?

I have changed the conductor plate, replace fluid and filter

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

What would make it shift into a higher gear when it should be down shifting

Submitted: 3 months ago.Category: Mercedes
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Answered in 4 minutes by:
12/31/2017
Mercedes Mechanic: Pete, Mercedes Mechanic replied 3 months ago
Pete
Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 31,762
Experience: Over 15 years experience as a Mercedes dealer technician
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Hi, my name is ***** ***** I will be happy to assist with this today.In some cases, I may need more info to assist better.I apologize for any delay.

This code sets when a fault is detected with the electronic accelerator actuator.This is part of the throttle body itself.In some cases, it is just carbon build up in the throttle body needing to be cleaned out to resolve this issue using a shop rag with carburetor or brake cleaner sprayed on it.

In other cases when cleaning it does not work, it will need to be replaced as a complete throttle body assembly.

When this fails it will cause transmission shift issues like you see here.

It is M16/6 in the diagram below

https://www.dropbox.com/s/ypp5wi43isa4phu/act-12-31.png?dl=0

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service, your 5-star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.I work on delivering the best answer and help here but in some cases, it can be difficult to do without seeing the vehicle.

Thanks Pete

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Pete, Mercedes Mechanic
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Satisfied Customers: 31,762
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