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2005 Prius main battery possibly going bad. Need help

Customer Question
2005 Prius main battery...

2005 Prius main battery possibly going bad. Need help diagnosing the issue.

Mechanic's Assistant: Did you test the battery with a voltmeter? And have you ever changed one before?

I did and yes, I have experience removing the unit and also have replaced a few modules in the past. The battery main terminals are reading over 200 volts even though the display is showing only one bar.

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

After the P0A80 code was set I removed the unit and probed each module to check for a low reading. At that time I found one module reading about 1 volt less than the others. I ordered a used replacement module and installed it. All the modules are reading close to each other at around 7.6 volts. When I drive the car the display jumps from say 6 bars down to maybe 1 or 2 especially on a hill. I can hear the engine racing to provide the needed power at that point. Coming back down a hill it charges back up to 5-6 bars again.

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

The last thing I did last night was hit the start button and the display was reading only 1 bar. I metered the main battery terminals and it read about 202 volts.

Submitted: 8 months ago.Category: Toyota
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Answered in 8 hours by:
9/14/2017
Toyota Mechanic: Eric, Automotive Repair Shop Manager replied 8 months ago
Eric
Eric, Automotive Repair Shop Manager
Category: Toyota
Satisfied Customers: 34,368
Experience: 20+ yrs. experience as repair shop manager and technician.
Verified

HI,

I am sorry that you have not been helped yet. I just came online and saw your question

Is the P0A80 code still present or did it clear after replcing the battery unit?

Just on the symptoms, I suspect the HV control module, but will need to know on the code, as well as need the last 8 of the vin to pull the schematics

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Customer reply replied 8 months ago

Actually the code has been set several times throughout this issue. I am resetting it with a handheld reader. But to answer your question, no, the code has never reset itself. Last 8 digits = 53019672

Toyota Mechanic: Eric, Automotive Repair Shop Manager replied 8 months ago

Ok, there is a service bulletin out for this code due to cooling fan being clogged with dust and debris.

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Customer reply replied 8 months ago

The cooling fan, when it is on is moving plenty of air over the battery. Actually right now the battery is open with covers removed so I don't think that the fan is the issue. Plus,this problem with the voltage display dropping is happening immediately upon driving when the car is very cool inside. One side note, the fan does come on whenever the P0A08 code is set which I think is normal from what I have been reading. I can clean the fan and ducting but I find it hard to believe this is the root cause. I have never seen any other codes set regarding this issue. One clarification to my original statement about the voltage reading is that I took the reading at the battery terminals ahead of the output terminals with the car turned off and read 202 Volts. When I then press start the display was reading 1 bar. You mentioned something about the HV controller; is this controller mounted in the HV battery compartment?

Customer reply replied 8 months ago

Relist: Inaccurate answer. Please submit to a different expert.

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Eric
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Eric, Automotive Repair Shop Manager
Category: Toyota
Satisfied Customers: 34,368
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