Subcodes with Bluetooth OBD Reader?

P0AA6 is triggered by an HV leakage current. It is usually in the battery, but finding the leakage path requires visual inspection of the battery internals (corrosion/fluid leaks). The use of a "megger" (a very sensitive ohmmeter) to detect small currents can diagnose where the current path, but that requires a talented technician.

You need an app on your Phone or computer tablet that will show detailed battery data or subcodes. DRPius on android will show battery data in detail to see your battery health. The Official Toyota diagnostic software will show the subcodes but it is expensive unless you are willing to use a hacked version.

 

I could suggest searching the forums for Gen 2 Prius PID definitions that can be loaded into a ScanGauge II, Torque or similar phone apps, etc. There was a start on some common place and format for those but it never got really taken up past the collection for Gen 1. For Gen 2, Gen 3, and beyond, if you can find the PID definitions you will probably find them in something like a .xls file attached to some thread in some forum here.

In the collection for Gen 1, I see somebody did successfully find the PIDs for five INF codes slots (probably vincent1449p, who did a lot of that work). If you can find Gen 2 PIDs for them, you're probably in business, as long as whatever app you are using with your OBD reader lets you define custom PIDs.

 

How did you get the Techstream software? I've been looking online but every website makes it seem very convoluted.

 

I believe that it actually is possible to build an Android or iOS smartphone app that could use a standard cheap AliExpress ELM327 dongle and read the subcodes, if anyone would implement the codes, which seem to be available here: rentry.co/prius-inf-subcodes
Now while I am not the best software dev myself, I know enough to see the pieces. I cannot think of any good reason why a free open-source reader could not do what Techstream does?

 

Why would you expect a developer to spend several hours of their time creating an app and then make it available for free?

 

Because
1) to help the community of DIY Toyota Repair Enthusiasts the flourish here on Priuschat
and
2) it can be done pretty much for free these days with vibe coding engineering

 

Its hard to compete with Techstream for free

 

Sure is indeed, and that's not the goal. The goal is to do the one thing Dr. Prius, Torque, and every other phone app currently cannot: read the INF subcodes. Not replace Techstream, just fill the gap between "buy a Mini-VCI and find a Windows laptop" and "guess."

 

The Autel above in bluetooth

 

The INF codes for P0AA6 just help you by narrowing your search into one of these four areas:



If you don't have the INF codes, you just have to do that first step of narrowing the search yourself. There's a pretty systematic way you can do it (with the code cleared, then IG ON, then READY in neutral, then READY in gear, then with A/C on), which you can read a lot about in Gen 1 threads here, because Gen 1 didn't give those INF codes yet, so it was what you had to do. (Minus the part about A/C, because Gen 1 didn't have electric A/C, and also you'll be looking for threads about P3009 because the standard P0AA6 code came later than Gen 1.)

 

UPDATE: I believe I’ve now worked out how to read Toyota INF/detail codes from a Gen 2 Prius using nothing more exotic than a bog-standard Bluetooth ELM327 adapter ($3.50 on AliExpress). That’s a great step forward!

But reading is not the same as decoding, which is the real end goal ofcourse...

While I’m a pretty shitty, but aspiring, Prius mechanic, this community has helped me keep my car running over the years, so I like to try and contribute back here. I do have a degree in computer science, so this part is much more my territory. Especially with Claude doing a fair bit of the detective work.

The missing piece is real-world data of a Prius Gen2 with active fault code stored. Right now I only have one Gen 2 to test against, so I’m looking for volunteers with 2004–2009 Priuses.

A car with an active stored fault would be particularly useful because that would help me build and verify the INF/detail-code decoder. P0AA6, P3000, P3019, or really anything with an INF code would be great.

But even if your Prius has no current faults, a capture would still help. Data from different cars and model years will let me verify that the underlying read method works consistently across Gen 2s rather than just on a single sample.

I’ve built a small Android app specifically for collecting these captures. It’s an APK, so Android only, version 8 or newer. You’ll also need a Bluetooth ELM327 adapter.

The process is simple:

1. Install the APK on an Android 8+ phone
2. Connect your Bluetooth ELM327
3. Run the capture
4. Tap Share to send me the raw data

It should take about two minutes.

The goal is to use these real-world captures to build and verify the decoder and create a crowdsourced dataset. The app, decoder, and findings will be released as an open-source GitHub project so Gen 2 owners can eventually read this information without Techstream or a Mini-VCI setup.

So if you have a Gen 2, triangle or no triangle, an Android 8+ phone, and a Bluetooth ELM327, I’d love to borrow about two minutes of your Prius. If it has the triangle on, even better.

DM me!