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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4819
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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I have a 2006 Prius with Fault codes P3190 and P0A80 error

Customer Question

Customer: I have a 2006 Prius with Fault codes P3190 and P0A80 error codes. Red triangle master Caution on. Believe failing high voltage battery the cause. Carefully replaced existing high voltage battery with replacement battery. Cleared ECU error codes. No error codes now show in ECU. No error codes show in MFD in diagnotic mode and all are OK. However Red triangle master caution will not go out. The MFD shows car with "!". Still no ECU but codes to clear. I think the car is ready but some ECU function needs a reset to allow the car to acknoledge the new battery.
JA: Thanks. Can you give me any more details about your issue?
Customer: The old high voltage battery was weaker and weaker and finally the car died on the highway. T
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Customer: There was two icons on the main LCD the red triangle and red main battery and MFD red car with "!". Clearning ECU codes allow the car to drive about 1 mile and then the 3 errors returned. Cleared error codes a second time and car to move 1/4 mile and then died. Had AAA tow car back. Most likely cause was bad high voltage battery. Replaced high voltage battery with on from salvage yard from running but crashed Prius. Cleared ECU errors after battery swap. The red main battery light is out but the red triangle remains, MFD still shows red car icon with "!". There are no ECU codes to clear but all appears ready to run. However, I do not know how to clear red triangle or red car "!". Is there a special code reader that is needed or a special jumper on the OBD2 pins that can reset the error codes? Or are the red triangle or red car "!" remaining problems that can be solved with no ECU error and no MFD in diagnotic mode and all are OK. My background is Mechanical and Electrical engineering (power electronics and high voltage) so I can easily work on machanical and electrical systems but there is little I can do with hidden codes. What would you recommend?
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Submitted: 1 year ago.
Category: Toyota
Customer: replied 1 year ago.
I just checked the 12Volt battery and it shows 11.4 volts with the over head light on. Could a low 12 Volt battery cause problems resetting an errors? I will put the 12 volt battery on a charger and see if this can help the problem go away.Mark J.
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. A low AUX battery will cause you all kinds of bizarre issues. Please do NOT charge the AUX battery with more than 2 amps on a trickle charge, you will cook the battery. More often than not, a low AUX battery will not come back to a full state of charge, especially if the battery is 3-4 years old (or older). If the AUX battery is 3 - 4 years old, I would recommend you replace it, clear the codes and then proceed form there. Speaking of codes, the Prius self diagnostic system relies heavily on "sub codes'. Not all scanners can read Prius sub codes. Before you do anything else, I would get a Toyota dealership service department to scan theis car and check for sub codes.

Expert:  Toyota Service replied 1 year ago.

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Customer: replied 1 year ago.
Hello I already have the 12 Volt battery charging and already have the 2 amp setting. I agree with any 12 volt battery below 12.0 Volts, low current charging is required and I always start at 2 amps first. The battery is rather small and was probably depleted during the first failures with the lights on. I will make sure the 12 volt battery is at 12.6 volts or better and if not first replace the 12 volt battery. Then the errors may go away or I can continue to solve the problems. I cannot move the car to a dealership without having it towed again. Is there a recommend sub-code reader I can buy or borrow without towing the car again? Mark J
Expert:  Toyota Service replied 1 year ago.

I do not know of any inexpensive scanners that can do sub codes. I believe that the only one that can (aftermarket) is the Snap-on Solus unit (but that is over a thousand dollars).

Trickle charge the Aux battery and retest for codes in the morning.

Customer: replied 1 year ago.
Hello, thank you for your advice. My continuing checking on Prius issues is the low 12 volt battery is a huge problem, the computer cannot really tell me what is wrong. If the 12 volt battery is not good, I will replace it and continue to solving problems from there. Bad news on the scanner. Long ago I bought a Tech 1 for about $1800 so I work on all the older 80's and earlier 90's cars but I thought ODB had solved most of the issues. With proper 12 volt power, all problems may clear or hopefully the car will reveal any new codes. I will let you know. ***** *****
Expert:  Toyota Service replied 1 year ago.

Correct. the 12 volt Aux battery is responsible for powering up all of the onboard electronics. The self test (performed during the power-up sequence) can fail (set a code) due to a weak aux battery.