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I could not find your last answer so I copied and pasted our next to last conversation:
Question:  QUESTION: Hi Eric,
You had assisted on a question on this dishwasher literally I think right at or on Christmas.  Sorry I did not leave a rating...things just got hectic.  I will be sure to do so this time.  Always a "10"!  My question:  Over Christmas my dishwasher was not draining.  Just a clogged drainage hose.  I am now receiving an error "UO" or "U0" (zero).  When starting it makes a noise like a heartbeat a few times then stops.  (ironic, I know) Then the error code comes on.
It's a "Professional Series" 4300.  Model #: PLD4555RFC0 Serial #: TH74087120.  Thanks for any life support you may be able to render!  Andy

ANSWER: First thing would be to check the electric drain pump and be sure nothing go inside and damaged the impellers.  While there, Make sure the drain pump is actually working. Verify there is no blockage and the pump is actually running without a broken or worn impeller....

Waiting to hear from you,
Eric and Ann Campion

---------- FOLLOW-UP ----------

QUESTION: Thanks.  I did take the pump apart about a month ago before I realized the drain hose was clogged.  Now, yesterday, there was some water build up in the bottom, (which I think occured because it does run briefly before the error message occurs) but I hit the start button twice and it drained just fine (and quickly) so I think I'm ok there.  thanks
Answer:  So now the unit is in fact draining....After doing so me more research, the Error UO error code means "Vent Open". The display cannot make the letter V so it uses the letter U.  On the top back right corner of the dishwasher tub, there is a vent and fan that opens to help dry the dishes at the end of the cycle. If the computer senses that the vent is open, then it won't start the cycle. Frigidaire says to first check the wiring and connections. If the wiring and connections are good, then you should first replace the vent assembly. If that doesn't solve your problem, then you should replace the main control board.  Aren't you thrilled with the Frigidaire resolution to that error code?  

Part number for the vent/damper assembly is 154562802.  I can sell it to you for 102.95 in new only if interested.  If I can help further, I am here.  

The new issue I was last having is no water going into the dishwasher.  I check the water going into what I believe is the pump. Stainless hose going in, no issues there.  I removed the pump and could only access and see a screen... no impeller/propeller.  I could not get the black rubber hose from the pump to the body of the dishwasher off for fear of breaking the connection.  I ran the dishwasher and it did not feel like there was pressure in that hose, leading me to believe there is an issue with the pump.  I checked the wire connection too. Seems odd this would occur right after the "vent open" error code. They were hard to read but here are the numbers I read off the pump. (I think) C20407 and 33129013.  Think it might need this little pump?  Thanks.  Andy (this is a different "pump" than mentioned earlier... it is a small white pump (I guess it's a pump) on the lower right front side of the washer)

Actually the 'little pump' you are referring to is actually a water inlet valve.  It is not a pump and does not pump water.  It it simply an electric faucet ,so to speak.  The dishwasher supplies 110 volts to the valve and a magnetic coil energizes opening the valve at which time the water pressure at your home pushed the water through the valve until there is enough water in the dishwasher.  Just like your kitchen faucet.  Open the valve and water comes out....close it and it stops.  If you apply 110 volts to the valve, it will open and water will flow.  Are you able to do this?

Waiting to hear from you,
Eric and Ann Campion

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Eric Campion


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