P3107 After Crash

I would be cautious about that assumption, as I am not seeing anything that would suggest a problem communicating with the airbag ECU would have any connection to the choice of driving modes. Where have you found that information?

That depends ... are you looking in the PDF of a 2010 liftback manual that kind of circulates on the internet? That one was made by people doing lots and lots of print-to-file while signed in for repair manual access on TIS, and glomming all the little PDF files together, and there are whole sections they just missed, including the one for P3107. That'll make it kind of hard to follow the troubleshooting steps. Also, the whole SUPPLEMENTAL RESTRAINT SYSTEM: AIRBAG SYSTEM portion of that PDF came from a Gen 2 repair manual by mistake. That also will complicate the troubleshooting.

So this might be a case where going to one of the better sources and using your actual model's and year's repair manual will save you a bunch of head scratching.

Toyota Service Information and Where To Find It | PriusChat

While the airbag ECU and the power management control ECU clearly communicate about some things, I don't believe the airbag ECU needs that communication to be told when to inflate the airbags; it's got its own sensors for that. (It does, of course, use info from the occupant classification ECU to decide about inflating the passenger airbags.)

While I'm thinking about it, has the airbag ECU been replaced since the crash?

 

You can check that. Search the PDF for P3107, looking not for random mentions of the code in lists or other sections, but for its full troubleshooting section—the section whose first page has a description paragraph, diagram sometimes, then a triple box of DTC No., Detection Condition, Trouble Areas, then Monitor Description, Monitor Strategy, Enabling Conditions, Malfunction Thresholds, Operating Range, Confirmation Pattern, and Inspection Procedure. If you can find that section, you're looking in a less-sparse PDF than I am. (You can browse around the manual to see what those sections really look like for other trouble codes where they aren't missing.)

Similarly, search your PDF for SUPPLEMENTAL RESTRAINT SYSTEM: AIRBAG SYSTEM (spelled just that way, space after the colon, no space before), and, when you get to that page, are you looking at a drawing of a Gen 2 Prius, and does the page footer say 2004–2009? If so, and you flip the following pages of that section, you'll find they're all from a Gen 2 manual.

Airbag ECU, SRS module, Air bag control module (what Toyota calls it in the parts list), and Center Airbag Sensor Assembly (what they sometimes call it in the repair manual) are all names for the same gizmo.

I asked if it was replaced after the crash because I believe it is designed to be one use. Toyota intends that it be replaced after any severe-enough crash. If there's been a crash where it deployed the airbags, I believe it definitely limits communication afterward, on purpose, to force replacing it. That might explain the P3107. I'm not sure about a story like this, where the bags apparently were not deployed. It might depend on the severity of the crash, and whether the ECU really decided the bags weren't needed, or it wanted to deploy them but they didn't inflate for some other reason.

While Toyota intends for the thing to be replaced, I think there are some businesses you can send it off to for a reset.