Advise - Gen 2, Dealer says needs Hybrid Computer, maybe battery

how many miles on her? have you talked to the battery installer?

'newhybridbatteries.com' $1,600. call around, some dealers are under 2k for an oem

member eric becky is in madison, he's a prius expert

 

you are. it's a matter of reading the codes and troubleshooting with the service manual. some dealers are better than others

 

Since you have no easy way of reading codes, before you throw away a bunch of money, try disconnecting the 12v battery for a minute. That will reset all the ecus to default. Then reconnect it and see if the car will work.

If it does work, then you most likely have a HV isolation fault. That code will prevent the car from going 'ready' after it is shut off. If the code comes in while driving, it will allow you to continue driving normally. But, once you shut the car off, it locks out the ability to go 'ready'. Luckily it can be reset by disconnecting the 12v battery. Some people have been known to install switches at the 12v battery to allow rapid reset and continue driving the car for years. This fault is usually caused by a minor electrolyte leak/seep from one of the battery modules. Obviously, HV battery replacement would solve the problem, as long as the HV battery was the source of the problem.

Later years (after Gen 2) no longer have this fault lock out the car. It remains drivable.

Other things to think about...

If the dealer diagnosed the car, they should be able to provide a report of what the codes were, along with subcodes. You should get that info and post it.

Don't get suckered into a bunch of repairs without having the 12v battery verified to be in good condition and properly charged. Remember, the Prius is a rolling computer where the computers work on a 12v battery. How well does your household desktop computer work if the wall plug is falling out? Similar situation for a Prius when it has a poorly performing 12v battery.

 

I don't recommend driving forever on a reported isolation fault.

The reason is that one leakage path to the chassis isn't much of a big deal; the computer can detect it, lets you know by a code, and you can (carefully!) open things up and clean it.

However, if conditions were right for one leakage path to form, they are probably right for another one to form eventually, and that would complete a circuit. How far apart were the modules forming those two leakage paths would partly determine how much power gets delivered into that completed circuit.

So, while the first code reporting an isolation fault isn't necessarily a hair-on-fire urgent event, I still recommend treating it as a "plan to get in there and take care of it" kind of event.

 

To disconnect the 12v battery you need a 10mm socket, 3" extension and a 1/4 or 3/8" ratchet. Simply remove the negative grounding screw on the negative battery cable from the body. There is no need to remove either cable from the 12 volt battery's terminals. At the 4:34 mark in this video you see the negative cable

Here are a couple of how-tos for the 12 volt battery test.

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Get the codes and sub codes from the dealership's scan and report back as you previously indicated.

 

Gotta' know the codes.

Suspect the battery first, Prius ECU's failure rates are very low (it's usually a burned out wiring connector to it).

GOOD LUCK!

 

The codes all look consistent with the dealer's story. P3000 is just the car's main coordinating ECU (it has different names in different generations) saying "hmm, something's up with the battery ECU". C1259 and C1310 are both from the brake/skid ECU and only mean "hmm, coordinating ECU told me something's up". I haven't looked up U0100 specifically, but U codes are always something-can't-communicate-with-something. And no codes in the list from the actual battery ECU.

 

Just another set of eyes on your throw a rebuilt in for $850 plan. For what you have already spent plus what you plan to spend you could replace with all new (aftermarket) modules from newpriusbattries.com. They are $1600 delivered to anywhere in 48 mainland states and 3-ear warranty, but some assembly is required. If you don't need to rush into a decision, this would be a better solution. If you are not up for DIY, NPB can recommend a local installer to do it for you. It could be worth a look. If TMR-JWAP's suggestion works for you, it could buy you some time too.

 

i'd go with the oem at that price. either way, it will be substantially lower than the dealers 4k.

 

Have you spoken with @strawbrad already?

 

None of those codes confirm a bad battery. A voltage leak is the most likely source of the not going into drive problem but that code is not present.

Did I replace the battery in Feb 2019? Can't tell from just your screen name.

 

They seem pretty consistent with a bad (or at least offline for some reason) battery ECU though.

Specifically, the P3000 (HV ECU saying something's up at the battery ECU), combined with the battery ECU having nothing to say for itself.

The U0100 is a communication error, but it's communication between the HV ECU and the engine ECU, so it's nothing directly to do with the battery, but might indicate some more general CAN flakiness going on.

 

If your state has normal 48 state emission/inspection requirements, there are many places on ebay that sell replacement cat systems at reasonable prices. ~135 bucks for just the cat portion that bolts to the exhaust manifold and splices to the resonator or about 350ish for a complete assembly that bolts to the exhaust manifold on one end and bolts to the exhaust pipe at the rear passenger side just before it goes past the rear wheels.