Where to start? ECU or HV voltage discrepency?

Welcome to the world of Prius. It sounds like you realized the Prius would be a 'project car' and that attitude is the most important for where you are headed. Rather than deal with the overhead of quoting, I'm converting your comments into italics and mixing in my thoughts . . . there are other excellent, "good Prius friends" who may have details that I might miss:

I recently purchased a 2001 prius that needs work. I am excited to get it back on the road. I began reading priuschat even before I bought it. This appears to be a great forum, and I have all ready learned a lot.

Excellent start but I would also recommend joining the Yahoo Group "Prius Technical Stuff" because of the message archives that go back to November 2000 shortly after the first NHW11 Prius arrived. You might also think about ecomodder.com, an experiments place.

The prius currently has the TOD and CEL lit. I can unplug the 12v and the lights will go away for about 4 miles. Then they return along with the red car with a ! mark. If I drive about another 2 miles the brake light comes on. at that point the ICE begins to rev really fast. The car loses acceleration, but it will allow me to keep driving. The Energy screen shows that no charge is coming or going to the HV. Mpg is about 30mpg,

Obviously, something is still broke so the first step is to have an OBD system help read out the codes and sub-codes. There are three options:

• $150 Scangauge II - more a driving aid, Vincent1449 has done a wonderful job of posting XGAUGEs needed to look at the most critical systems.
• $500 AutoEnginuity - a diagnostic tool that attempts to replicate the TechStream-lite functions.
• $400+$55/day rental Techstream-Lite - I have not used this so I don't have 'hands on' to share.
• $0 - flash codes, requires using jumpers and in some cases, an extra LED, provides basic code readouts.
• over-the-counter readers - they don't know how to read Prius systems including traction battery voltages.

I had codes ran the day I brought it home. The part store guy did not give me the codes, but said it was regen brake fail, missfire, uneven hv level, low battery block 6 and 10. I would also like to mention that the previous owner claims to have just changed the 12v battery.

Now you see the problem with 3d party reports of a scan. They had a Prius-aware scanner and you'll never really know if you've fixed a problem and not induced another without your own scanner. But "low battery block 6 and 10" begs the question, 'how low?'

A single NiMH cell has a nominal 1.2 V level. If there is a failed cell in the 12 cells that make one battery block (aka., two, 6 cell modules), the signature is a 1.2 V difference. Replacement is the only option. However, if it is just 0.3 V off, it means marginal but not yet failed hard.

I got the car home and cleaned the MAF cleaned the throttle plate and replaced the spark plugs. The plugs where really white and worn. took it for a test ride and the same problems persist.
I then had the codes rerun. this time the misfire was gone. the new codes are C1213, C1259, and I a P300? code. I believe it was battery unbalanced charge.

We need to know the voltages of the traction battery blocks to make that call.

So where to start? ECU or HV or 12V??

The following shows you made the right choice:

I thought I should also double check the 12v. The on screen voltmeter only reads 11.5 at rest 11.0 with lights on and 13.2 when running. Yet if I check with a voltmeter at the battery I get 12.4 at rest 11.8 lights on and 13.8 running. Could the internal voltmeter be that far off? or is their a current leak?

These are normal voltages and a good thing:

• 11.9 - 12.8 V - rest, 12 V battery range for a good battery, no load
• <11.9 V with load - battery could be weak but the 11.0 does not set my hair on fire. Check ground wire for corrosion or oxidation, buff with sandpaper, and reinstall.
• 13.8-13.9 V - the DC-to-DC charger is working fine. <relief!>

Considering 2 of the codes are ecu codes, does it need to be replaced? It currently has a 47054 ecu.
OR in your opinion will fixing the HV solve the ECU code problems?
The HV definetly needs to be fixed. I plan on removing it myself rebalancing, and replacing the bad cells. I saw on the forum that some people approve of the Ebay seller that is selling tested cells for about $30. If I have to bad blocks do I need to order 2 cells or 4 cells?

The problem is a failed cell will run hot and this will weaken the modules on either side. This is why you need these metrics:

• 19 battery block voltages - how bad is it?
• 4 traction battery temperatures - how bad is it?
• MG1 and MG2 temperatures - to make sure these are OK.

Any input as to what my next step should be would be helpful.

1. $200-300 - shop manuals, volumes 1 and 2 and schematics or TIS subscription if you prefer to 'rent' them and read online. These will also tell you what the different codes mean and the 'ambiguity group' or things to check. It is much faster and reliable than asking the 'gray beads' who hang here somedays.
2. $500 - AutoEnginuity since this is a 'project car' or Techstream Lite rental, you may get by with less expensive Scangauge II and adding XGAUGES as needed for specific subsystems.
3. Survey and diagnose all ECUs for which you have a scanner.

GOOD LUCK!
Bob Wilson

 

Most of the ECUs have a blink-code option; the steering ECU is the one that has a blink code option but is missing a light to blink, so needs a resistor and LED supplied. Two ECUs that unfortunately don't do blinks and will only talk to a Prius-aware scanner are the HV and Battery ECUs (there are also ScanGauge II XGAUGEs that have been worked out for these).

As I recall, C1259 is a code that is logged by the Braking ECU whenever it is aware of any trouble code at all in the HV ECU (they talk, because braking is coordinated with the HV powertrain). Once any underlying HV issues have been taken care of, you should be able to clear the brake code and not see it come back.

I have that feeling that I ought to remember what C1213 is but at the moment I don't, and my manuals are in the car. I do recommend either getting the techinfo subscription or ordering the printed books.

-Chap

 

One thing's for sure, codes don't lie do they.

No, don't balance based on resistance. First of all, resistance can't be measured by a meter if voltage is present and voltage is present in a battery.

If you really want to balance them correctly, you have to do it on capacity. This is done by charging and discharging the cells, individually, 2 or 3 times to measure capacity. Then you match cells by pairing other cells w/ the same capacity. This is a long process and will require a charger/balancer similiar to a Supermate DC6.

Now, I will give you a second option (that I don't advocate but believe will work). If you use this option you assume all risk. There really is no risk other than having to go back and do it the right way (matching by capacity). Also, if you use this option, please report back to us with updates, good or bad.

1) Start by labeling all your cells 1-38
2) Remove the two bad cells and replace them with two of the recently acquired cells (transfer the numbers from the removed cells to the "new" cells)
3) Hook up all cells in parallel for 24-48 hrs (the longer the better, this will balance cell voltage but not capacity)
4) Reassemble and reinstall the battery pack
5) Drive the car and report the results

The likely results will be smooth operation for a while (a while could mean 1 week or many years depending on whether or not you get lucky and happen to match capacity). Worse case scenario is you will have to do capacity matching if the codes come back.

 

When it comes to dealing with battery packs and balancing, nothing is quick and there are no magic bullets. Good luck.

 

Brilliant!

Bob Wilson

 

From my experience ,I would say you have another module going bad. It has all the symptoms of it. It depends on the terrain If you have hills to climb the weak module will discharge quicker and throw the code. If you drive it on level ground at consistent speed the weak module can some what keep up with the others. Just my 2 cents.

 

It's getting hard to find good used Gen1 modules. I'm afraid you may be entering "whack a mole" territory.....you replace bad modules...car is ok for a while then another bad module POPS ITS HEAD UP.

I've BTDT. The first time is fun for learning. After you take apart the same battery 4-5 times it gets old, especially the 900 or so screws in the battery assembly (ok it's not 900 but seems like it sometimes) and block 19 (easiest one to replace) never seems to fail, it's always blocks that require removing 800 of the screws.

If you like the car, start looking for 1.5 Gen2 packs as donors.
Ideally you can replace all the cells with similar Gen2 modules from a lowish milage wrecked Gen2 and you'll get years of service out of the battery.