'02 Prius, Not starting, P3125 Code

There is only way now to charge the high voltage battery while in the car is with a high voltage battery charger or put in another hv battery that is charged. It sounds like your battery is OK but just discharged. I know it sounds crazy but you cannot turn over the gas engine to troubleshoot it because the battery is low and you cannot charge the battery because the gas engine will not start and run. The small 12 volt battery does not start the car, it only pulls in a relay that allows the hv battery to start the car.

Roy

 

You can buy the charger for your car by looking on this site for a supplier - hope someone else will jump in to tell you the name of a supplier near you. I use a hv charger that I built myself and it charges through a small connector in the trunk of my car. I use it when I run my battery down. Hope this helps

Roy

 

If you hybrid battery is low you have to deal with that first.

A Prius hybrid battery charger is a lifesaver!
Looks like the PriusChat shop only carries the 2004-2009 charger.

I can sell you the charger for your Gen 1. It is higher voltage than the Gen 2 chargers (so it is more expensive unfortunately).
Right now the price is $569 +$20 shipping.
This is the discharge ready version so it will be forward compatible with an automatic discharger should you ever wish to get one.

It is a special order item and takes 4-5 days before it will be shipped.
Call me and I can talk with you about it and send you some info.

A discharged hybrid battery sucks! Most dealers do not even have a charger.

Once you have this, the charger harness will be permanently mounted in your car and you can use it as a maintenance charger to periodically balance your pack. Just hook it up to your charger once or twice a year as a preventative measure.

 

Eric sounds like he comes up against your problem on a regular basis as he is in the business of rebuilding the hv batteries and has given me good advice through prius chat.

The original 2001 prius used in japan came with a charger that connects to a small connector on the battery. My 3 2001 prius cars all have this connector I believe your 2003 does as well. This connector connects directly to the hv battery- be sure any charger you buy will allow you to plug into this convenient connector. With your mini vic you will be able to monitor the charging process to see the battery voltages rise and the percent of total battery charge. Once you can get the battery voltage up to start the car you can troubleshoot the gas engine problem. If you towed the car with the front wheels down over 30 miles an hour it may have created a problem in that it could generate a voltage that would be fed back to the inverter, hope this did not occur. Most tow truck drivers know not to tow this way. Except for the battery discharge problem I have found these cars very reliable so do not get discouraged.

Roy from Canada

 

If you can post screen shots of the Techstream pages, many of us can then look at the images and share what technical details we are looking for. For example, the battery status includes the State of Charge (SOC). I suspect your traction battery is low but still high enough to support some restarts.

I am also interested in seeing the HV ECU screen shots so we can look for the subcodes and other metrics.

Sharing screen shots puts the information in front of experienced eyes.

Bob Wilson

 

Mine came with a full size CD.

 

MG1 will spin engine but MG2 will keep Prius from moving when doing it. Prius engine uses atkinson cycle and probably wouldn’t start with slow cranking of 12V starter. Also any other starting method to start engine without starting motor with automatic transmission (like using drill) would spin engine too slowly to start it. And hybrid system wouldn’t allow engine to start even if you somehow could get it to spin fast enough. Only way to start it is to charge hv-battery with external charger.

 

You have a general understanding but some details are missing. The car is operated by half a dozen control computers. For example, there is no throttle cable. The accelerator changes a pair of variable resistors connected to the transmission computer. That computer tells the engine computer what to do.

The miniVCI gets the car status from the control computers which is why the screen shots are so important. This car is a real puzzler but rewarding to the curious and persistent.

Bob Wilson

 

Jumping may and probably will damage both Priuses. You could use methods to slowly charge battery pack by taking power from working Prius. But I’m not going to give you instructions since you may kill yourself doing that… And it really wouldn’t be much harder to build your own grid charger to charge hv-battery.

Yes you can measure MG1 and MG2 just like normal electric motors to get good readings you need low impedance meter. And still you cannot be sure that there isn’t problem…

Can you spin engine from crank bolt? If you can then at least engine or MG1 isn’t seized.

 

Jerry said when the engine tried to start the vehicle lurched forward. Is that a clue??

 

You could theoretically attach her battery in parallel with yours to charge it. A total of 4 connections. Two on each battery.
Pretty easy to make a mistake and actually kill yourself so be careful and follow safety precautions for handling high voltage.

 

H

Yes it is. It indicates his shift mechinism is not in park, in a manual I have it indicates there is a mechinism in the transmission area that has not gone into position leaving the car essentially in drive, it says to put on the emergency brake to get around this to remove your key. This is a long shot but very quick to try.

Yes it is Dane-- The car is not in park. Jerry -- try this - put on the emergency brake put in the key and try to start the car . This comes from a toyota instruction course I found on line, it indicates there is a problem with the shift mechanism and putting on the emergency brake will allow the key to come out. You indicated the key was locked and the only way to remove it was to disconnect the battery which is the indication that you were not in park. Hope this helps.

Roy from Canada

 

You shouldn’t connect hv-batteries like that. It can damage both of those batteries and if they have (gen2 does have) fuses in them burn the fuse.

 

Yes, Gen 1 also has a fuse.

It's good to remember that the computers in normal operation strictly limit the amount of current into and out of the battery based on all kinds of things such as state of charge, internal resistance (from which ohmic heating can be calculated) and actual measured temperature, and pretty much never allow it over 100 amps under any conditions, and that only for very short periods.

If you take two powerful batteries, one at a high state of charge and one at a very low state, and slap wires between them, there is nothing limiting the resulting current except the battery internal resistance, the size of the wires, and the fuse. Bob Wilson recently re-posted a photo that has made the rounds of a Prius battery after (even less violent) uncontrolled charging. It could be captioned, "you thought you had problems before?".

"Jumping" the batteries is not an attractive idea. Using a decent, purpose-built grid charger could be a pretty good one.

-Chap

 

IIRC, hydraulic formulas and electronic formulas are the same... only the names change. So, I've always likened paralleling batteries to a couple of buckets. Let's put a pipe at the bottom of two buckets that connect the two together. Now start filling the buckets. The water in each bucket will be at the same level. So far, so good.

Now make a hole in either bucket half way down between the top and bottom of the bucket. If you fill both buckets fast enough the you can fill both buckets to the brim. But let them sit and the undamaged bucket will now drain down to the level of the first bucket.

In other words, the undamaged bucket takes on the characteristics of the damaged bucket. It's not a whole lot different with batteries. If one is low in charge and you parallel a good one with it it should lower the charge in the 2nd. Now you have to increase the input to overcome the problem in now both batteries. That often exceeds the limitations of the system and bad things result.

 

All good advice. These are the usual precautions you should take when working with any battery, especially high voltage . I could never iterate each item.

Still it is technically possible if you know what you are doing. Just most people may not have the knowledge.

 

Uh OH! You are about to get hooked like this mechanical engineer did after buying our used 2003 Prius in October 2005. <GRINS>

The part you are describing is called a 'parking paw' and in our NHW11 is mechanically linked to the shifter. In "P", the shifter should be all the way forward. Your miniVCI can report what the HV ECU thinks the shifter position is.

The shifter uses a resistance network to inform the HV ECU what position is requested. Everything else is software controlling MG1/MG2 and the engine controller ECU power request.

Bob Wilson