Prius v: Multiple Warning Lights, Hybrid Battery Code, but 12v Disconnect Fixes it. Huh?!

Those aren't all battery codes.

B2799:

One of the following conditions is met:

• Error in communication between power management control ECU
  (HV CPU) and certification ECU assembly (smart key ECU assembly)
  or ID code box (immobiliser code ECU)
• Error in communication lines
• Communication ID is different between certification ECU assembly
  (smart key ECU assembly) or ID code box (immobiliser code
  ECU)*2 and power management control ECU (HV CPU) during
  communication

Caveat: that's from a Gen 3 liftback manual, you might want to double check in a manual for the v.

I do not find P1234 or C7777 in the liftback manual at all. I don't think the battery ECU gives any C codes.

I am always hesitant to say that 'off brand' code scanners are displaying those five-character DTCs incorrectly. I mean, that shouldn't be easy to do! The software sends a query, gets two bytes back, decodes them as four hex digits, munges the first one like this:



and done. It should be really hard for even the cheapest scan tool to be doing that wrong.

But I end up wondering if there are maybe checksums in the protocol (I knew once, but don't have time to look up again just now), and maybe the cheap implementations are flat-out forgetting to check those and retry messages that came noisy.

Kind of perplexing. Maybe P1234 and C7777 are real codes on a v.

 

I just did a quick scan of all 63 posts in this thread and see no mention of checking the health of the 12 V battery.
Before you waste any more time or money, you NEED to do that first.

 

Did you look in the repair manual specifically? Too many people say "I couldn't find anything on ..." when all they mean is they haven't looked in the obvious place.

Now, if they're really not in the Prius v repair manual for your year, that gets back to ... what on earth is Dr. Prius doing when it thinks it's decoding DTCs ... ?

 

I don't think I could find those codes in my "copy" of the repair manual. I think Toyota relinquishes that "work" to it's Techstream system.

moto g(7) power ?

 

I've never found a v Repair Manual (in pdf format) either. I think part of the problem is there was no hard copy version, so a nicely collated pdf has maybe never been compiled officially. Still, someone may have "cobbled" one.

 

That 12.7's with the car off, using a multimeter? That sounds good. The rest don't mean much.

 

Check.
The second one means that the charging system is working good.

 

Nah, they document the trouble codes very thoroughly in the repair manual. What's built into Techstream is nothing but fortune cookies.

... though if your subscription is active, Techstream can link you right to the section in the manual online.

But this wouldn't be the first time some oddball scantool has reported goofy codes. As I said in #63, I sure don't get it. Decoding four nybbles as hex and looking one up in a table should be pretty hard to mess up. But maybe some scanner software developers just have that talent.

 

Recall that not all codes are public, there may be legal issues once you get beyond engine/emissions.

For another brand car I'm familiar with (and for which they last published a written repair manual in 1998), the best scan software for owners for that brand is still uncovering codes and their meanings and diagnostic tree flow charts more than 20 years later. Active development took years and years with each release providing another layer of coverage of an area of the vehicle.

Scan tools intended for use by mechanics can often do more than read codes and give you a few words of description, they can often trigger actions via the car's many computers that help in the diagnosis. And at least one scan tool software package has multiple versions with the unlimited uses on an unlimited number of cars (repair shop version) being priced much higher than the enthusiasts version. It is also more capable. All for an engine whose rebuild can easily run $30k.

 

All of that is ... true ... and yet ... does not change the fact that simply displaying a DTC, whether you have heard of it or know what it means or not, is a matter of nothing more than getting a 16-bit number and mapping the two high bits onto (P, C, B, U) and the remaining 14 into hexdigits.

And yet, somehow, one keeps hearing of people using oddball code readers that somehow end up displaying codes that one never sees from Techstream.

Techstream has a lot of Toyota-specific knowledge baked into it, but not the kind of knowledge that changes what bits or hexdigits are.

 

The highlighted area of Block 7 tells you everything you need to know. That block has a failing/failed module. The other 2 blocks are on the way.

Take a look at the second photo, third line item. That's 'shortwave highest value". Its a measurement of the HV isolation from the rest of the car. 5 volts is perfect insulation/isolation. Most cars show 4.99V. Yours is showing 4.98V (which is fine), except for 4th column reading, where it's showing 0.03V, which is a dead short circuit between the HV system and the car chassis. Wonder what's up with that.

 

You might be able to clean the monitor contacts, I've never seen a bank at 12V that didn't have the mushy accelerator peddle.