Replace ECU when replacing traction battery?

To avoid ambiguity, could you pls request the part number and description of the ECU that is proposed to be replaced.

In general I do not believe it is necessary to replace any ECU when the battery is replaced. An exception might be if battery electrolyte leakage damaged the battery ECU.

The battery price does seem high and a cost-effective alternative might be to find a salvage unit and have an independent mechanic install it. As a variation of the above idea, an even better alternative (from a longevity perspective) might be to buy two 2G salvage battery assemblies (with 28 modules each) and pick the best 38 modules to populate the existing battery case. Good luck.

 

I'm not about to counter their diagnosis. However, I would recommend cleaning the throttle plate. The P3191, P3190, and P3101 all point to the engine and a sticky throttle plate would be consistent with some of your symptoms.

The NHW11 Prius software has to be changed by an EUC upgrade. However, both prices are pretty much 'retail.' If you are a 'do-it-yourself,' you could use salvage parts for a lot less and some sweat equity.

The battery leak does sound bad but there are other codes I would expect including one reporting unbalanced cells. My thinking is try the cheap fixes first and if the problem persists, it is time to make some hard choices.

Bob Wilson

 

the battery ECU does not need to automatically be replaced when replacing the battery itself. unless there is an issue with re-initializing the old one, it should be just fine.

 

I have an NHW 11 battery I bought at a salvage yard several months ago. I never used it because my problem turned out to be the inverter and not the traction battery. I have not tested the battery, but would be happy to if someone could let me know how. It's on my basement workbench collecting dust. The salvage yard guaranteed it to be in working condition. It had been my plan to replace the battery myself before I figured out my problem was the inverter. Looking at the manuals and forums, the battery replacement seems relatively easy. I would consider a DIY or maybe DIPY (doing it partly yourself) approach if I were in your shoes. Let me know if you are interested in the used battery... oh and it comes with the computer which is internal to the battery housing.

GW

 

The new battery doesn't come with an ECU in the enclosure, but the technician is supposed to transfer the old ECU from the old battery to the new one.

Art's Automotive have written a Gen I Battery Replacement article.

 

Some possibly relavent info from looking at the venerable Prius parts list. From 2001 to 8/01 in the 2002 model run the battery computer was part #89890-47030. After that #89890-47060, and on that list, sold for $983 instead of the earlier $1100.

What we often saw with NHW11 was that new computer part #s meant new programming, as they were not designed to be re-flashed. However this price drop suggests to me that something else happened as well (reduced parts count?).

None of that implies an old BECU would not drive a new HVB. It might mean that a new BECU could drive it better.

I believe there were no design changes to the HVB throughout the NHW11 model run - anyone disagree?

 

I also live in the Austin area and last year had your problem. Yes, they insisted that they replace the ECU (not the battery one) and all of the cables. Based on advice here, I declined replacing the ECU. The dealership's response? OK, well we won't warranty the new battery then.

The car runs as good as new with just getting the battery and not touching the ECU or the cables. Since the repair cost was half as much without replacing the ECU, even though they will not warranty the repair I still made the right gamble. At worst, the battery will die again and I'll break even.