2007 Red Triangle, ABS, (!) Random on/off

welcome!
grab tech stream diagnostic software on amazon for 25 bucks or so, and a compatible laptop.

if you need more help, the service manual is available at techinfo.toyota.com

 

The "more help" part is kind of a given; if you have only a code reader, the only information you can get are the codes and the little one-line "fortune cookies" that might pop up on the reader's screen about what the codes mean. A typical code's fortune cookie is of flat-out no use except as a memory jog to somebody who is already familiar from the manual with what that code really means. There will be a description there of the code's "detection condition", which tells you what actually happened to make the computer set that code. That's the information that's helpful, but it never fits in a fortune cookie, so you'll never see it just relying on a code reader. (Not even Techstream. Well, Techstream will give you a link to follow, but the link is into the manual so it will only work if your subscription is current.)

When somebody just takes a code's fortune cookie literally, like "all right, that one-liner has the name of part X in it, so I guess I need to replace part X", wasted time, money, unsolved problems, and disappointment often result.

Elektroingenieur helpfully put together a wiki page gathering a lot of ways of getting access to the manuals.

There's always the intermediate path of reading your codes and posting them here to see what other PriusChatters make of them. You'll get a bunch of ideas, and some of them will be better than fortune cookies. But then you have to figure out which ones those are.

 

Safest way is to get codes checked, preferably at a shop since i believe only techstream can read the brake related codes. What you can do right away is the check your oil level of your car, try to top off to full if you can, it will help the engine.

 

Since GirlWithGears has already expressed a preference for DIY over going to a shop, I would give similar advice only I'd say "read the codes" rather than "get the codes read". She can do that herself with the right stuff, and having the right stuff will make everything easier taking care of the car down the road.

There's another, really important step after "read the codes" and that is "find out what they mean from the repair manual" (more info). That's important because even though a code-reading device will usually display a few words about each code, those fortune-cookie displays are huge oversimplifications of what the codes really mean, and trying to rely only on them to fix a problem is a recipe for wasted money and effort.

There are even professional shop mechanics who fall into that trap, which means GirlWithGears's inclination to go DIY could even lead to better outcomes, depending on what the nearby shops are like.

 

Ohhhhh, yuck. I had never heard of that scanner. So it, like, combines reading your car's actual trouble codes with, umm, scraping the web for the most popular comments from clueless people about what they think fixed them?

Even in lockdown you have not got time for thash.

There is a repair manual (more info) with what the codes mean in your Prius and how to troubleshoot them and how to fix the issues.

U0129 is an issue with CANBUS communication between the HV ECU and the brake ECU. There should also be one of four subcodes to further pin down what kind of communication error was detected. The CAN bus does not use relays, and you don't have an alternator. The repair manual section on "CAN communication system" will step through what specific tests will find the problem. I don't remember if you said you have a multimeter.

 

Any updates worth sharing?