Freeze Frame Data Report

That is the FFD (freeze frame data) for a C1241. This DTC's fortune cookie one liner is "Low Battery Positive Voltage".

You will see that the report indicates +B1 is 5.88 V and +B2 is 5.72 V. Considering these should be in the region 12.9-13.2 V it indicates the 12 V battery is shot.

That would be the reason the battery was replaced, but it is only the small aux 12 V battery, not the HV battery.

That report shows no information about the HV (traction) battery.

 

No, there is only one 12 V battery. These are just two measure points that should be in the same ball park (which these are), if all is well.

 

Without knowing the test scenario, there's not a lot I could say with certainty.

 

Just that, all I can say is it looks like they were conducting a discharge test.

Without being able to look at the data live, it is hard to tell, for example, the voltage spread between the high voltage block and the low voltage block. But they look like they are tracking consistently with each other.

Unless you are having drivability issues, I wouldn't worry about it.

 

Are you saying that the report in your OP (original post) is after the recent battery replacement? What did they replace it with?

And just to clarify the "recent replacement" battery was which one?

If this 12 V battery is the one recently replaced and that report shows it is toast, I'd recommend the OEM or the Exide Edge AGM.

Do you own a battery charger?

 

It is.

All's well then.

 

I was wondering what the specs are supposed to be, thanks for that. Do you or anyone know where there is a manual reference posted anywhere for the related Parameters specification ranges?

 

That anywhere is here, of course:

Toyota Service Information and Where To Find It | PriusChat

Sometimes you have to use more than one of those resources to piece together what the different parameters are telling you. For example, the C1241 troubleshooting section in the Repair Manual will tell you what voltage levels will trigger the code. It includes a simplified wiring diagram, but it leaves stuff out that you find in the actual Electrical Wiring Diagram.

The Gen 2 Prius brake system has an especially maze-like wiring diagram, because (a) it is duplicated for redundancy (inside the skid control ECU are two copies of an ECU, with two of every connection to power, etc.), and (b) it is designed to run off the capacitor power supply in the back of the car if the normal 12 volt supply should fail.

So the skid ECU has: two always-connected battery power inputs, +B1 and +B2 (or +BI1 and +BI2 in some diagrams), independently fused on ABS MAIN1 and ABS MAIN2; two power inputs when the car is IG ON (IG1 and IG2, independently fused by ECU IG and IGN, respectively); two outputs from the capacitor backup power supply (OUT and OUT2), which go through ABS NO. 1 RELAY and ABS NO. 2 RELAY to arrive at the skid ECU as BS1 and BS2—but they also turn up there, before the relays, as +BO1 and +BO2 so the ECU knows how the backup power supply is doing, independently of the relays.

Those all normally have voltages you'd expect in a 12 volt system. It always bears repeating that when you get a code about one or more of them being low, it isn't always the 12 volt battery that's at fault. It can be issues in the wiring bringing the power to whatever terminal(s) might be shown as being low.

There are also two internal voltages, VM1 and VM2, derived from regulators inside the ECU. I believe those are normally pretty close to five volts, used to power the microprocessor circuitry. It takes a pretty big error on the 12-volt supplies to trigger a C1241 (has to be down below 9 volts or so), but only a very small deviation on the regulated 5 volts.

Oh, and also there's the ABS MAIN3 fuse, protecting the power supply to the capacitor backup. And the ABS 1 and ABS 2 fuses and ABS MTR 1 and 2 relays, supplying the pump motor.