Replaced pads and rotors, and now I've got "the codes"

I’ve never had a reason to try it, but it’s not clear to me that connecting terminals CG (4) and TC (13) of the DLC3 (OBD II) connector has any brake-related function on fourth-generation Prius or Prius Prime cars.

The Repair Manual (more info) mentions that method for diagnosing the airbag system, but not for the electronically controlled brake system, for which there are no “When not Using the Techstream” diagnostic instructions like those in the manuals for earlier models. The brake-related diagnostic trouble codes (DTCs) are also no longer listed with two-digit blink codes.

You may need a Toyota Techstream diagnostic system, or equivalent, for diagnosis, and definitely for complete bleeding of the brake system. If you just need to bleed the brake lines, however, there is a procedure that supposedly doesn’t require Techstream in the Repair Manual under Brake: Brake System (Other): Brake Fluid: Bleeding. This might not clear DTCs that have already been stored, however.

 

Apart from the lights/codes, how are the brakes performing?

My drill:

1. Disconnect 12 volt neg cable first.
2. When done pump brake pedal multiple times.
3. Reconnect neg cable. (There might be some "oddities" after, unusual revving during start up, two or three occurrences thus.

If the brakes seem fine, it might just require a dealership visit and a reset via Techstream, but I don't really know.

 

Have you tried disconnecting the 12 volt battery since the lights came on?

 

Failing to do the above, then starting the car, can cause codes. The car detects excessive brake travel.

 

It's not a matter of "the" ABS codes, it's about which of the hundred or so possibilities are the ones you've got. If Gen 4 no longer has the blink-em-out-on-dash-lights option, it'll take a code reader to find that out.

But brakes are common equipment in cars, so common code readers should be able to display those codes.

 

Dr Prius and a Bluetooth adapter is one of the cheapest options to read codes, maybe $10 for app and $20 for adapter. It claims to read codes, haven't tried it yet.

 

ScanGuageII is another item that might have read the codes, just fyi. I've had one of those for about a decade, all hardware, no phone involved. I do recall reading codes with it before. Vaguely...

They're a little pricey, and I had problems having one constantly hooked up, it was apparently causing (wait for it) brake errors, warning lights, and work-to-rule brake behaviour. At suggestion of dealership I removed it, and problem did not reoccur, so I guess they nailed it. I do use it sporadically, if I want to test something.

 

I recently saw my old ScanGaugeII kicking around in a box in storage. It was pretty hot technology when it came out.

Nowadays, I use a scanner I paid $188 for on Amazon a few months ago, though of course after the return period, I saw it on sale for $138. It successfully got my 2017 Prime to pair up with a factory-fresh blank Toyota key fob to the after a little fiddling with different menu choices and the timing of sticking the old and new new fobs on the start button during the procedure. So, it mostly paid for itself just from doing that, seeing as the dealer and locksmiths all wanted about $130 to add a new fob to the car's list of valid fobs. I was the guy whose fob self-released from the physical key that was all that was left on my key ring when my car was a few weeks old, and I'd been living dangerously with only one fob for almost 5 years! Back to having two working fobs now.

My particular scanner, a Launch Creader Elite 205, comes with 2 lifetime free "system diagnostics" packages and 5 lifetime free "reset features" beyond all the usual OBDII stuff, where it can reset any ODBII code, read and graph tons of parameters in real time, capture freeze frames, email you reports, etc. The included diagnostics are for ABS, and SRS (airbags). You get to choose 5 out of 15 or 20 reset topics. I took IMMO (fob to car matching), TPMS, ABS bleeding, SAS (steering angle sensor/calibration) and I think Electronic Parking Brake (Prime doesn't have one, but other cars in my family do). Or maybe I took something else as the last one.

Don't waste choices on things like Oil Reset that you can already do via the car menus. You can buy more diagnostics packages and reset features for something like $20/yr each. Ouch. But this was a good compromise at the time, a safe intro to advanced scanners, compared to a $500 scanner, $1000 scanner, or $1500 scanner. I think my next one will be $500ish. The Xtool D8 is on sale now for $559, so maybe it will break below $500 around Black Friday. Or maybe I'll grab the cheaper D7 instead. With ones like those, you're no longer at the mercy of mechanics or dealers for diagnosis of even deeply hidden things in all sorts of computer modules in the car, that never surface to a level where they'd throw an ODBII code.

As luck would have it, one of the diagnostic suites you have no choice but to take, is all about ABS and the brakes. While my Prime came up clean on it, it was really useful on my old Gen2: The parking-brake position switch had fallen off but still worked when I pressed it manually, plus a handful of non-OBDII brake/ABS codes were found to have been set (likely in the distant past) despite zero actual driving problems, including things like "Yaw sensor value out of range", "Roll sensor data missing" to paraphrase. I reset them all, and they never returned.