Quick flash of red triangle and beep sound

Were you accelerating, stopping, or turning a corner at the time of the flash and beep?

 

A quick triangle flash when starting up the car and no error code is usually a near dead 12v battery that needs a heavy charge or replacement.

A quick triangle flash when hard braking, accelerating or turning a sharp corner fast with no error code is usually because you're two quarts low on oil.

How's your MPG? How many miles on car? Are you behind on regular maintenance?

 

Dr. Prius only pulls a handful of codes, mostly related to the hybrid vehicle battery, so it is really inadequate for general vehicle diagnostics. It is no surprise that it reports no codes.

If you are interested in pulling all the codes your car may have, read the first few posts of ⇉ this thread ⇇ and then read the summary in post #37.

 

Wow, you must have really big hands... As in Dr. Prius deals with most common codes... It's designed as a first responder because you're smart enough to keep an OBD2 in your glove box... With practice, it's super easy to continue driving and plug in an OBD2 and open Dr. Prius App and get a basic sense of vital signs. If the problem gets worse and you have to pull over there's other apps for that in Car Scanner ELM and Autel's OBD system, as well as Toyota Techstream.

 

As of when it was reviewed in the thread dolj linked (and summarized in the later post dolj also linked), Dr. Prius was known to be able to show you trouble codes from the HV control ECU, battery ECU, and engine control module—that is, from three out of the dozen or so ECUs in a gen 2 Prius. It also has a number of specialized displays focused on traction battery performance. It can give "a basic sense of vital signs" to someone who expects the traction battery to be the major or only source of concerns in the car.

To be well-prepared with something in the glove box in case a warning light comes on for, say, the brakes, or steering, or other systems in the car, it's advisable to have one of the less-specialized apps that can show you the rest of those codes.

If the capabilities of Dr. Prius have expanded since it was last reviewed in that thread, that would be useful information to add there.

 

In 8 years of using it to help people with many, many Prius I can only think of two instances it wasn't useful as a first responder, which turned out to be a 1) brake caliper out of position and 2) leaky vacume hose. In all other instances it was all I needed to know what the problem is.

 

So, all of the other problems you found must have been related to a problem reported by one of the three ECUs that the Dr Prius app is capable of communicating with. Very interesting information.

 

It seems then as if the selection of problems you ended up helping people with was skewed toward those with trouble codes in the ECM or HV control or battery ECUs, the only ones Dr. Prius can show you codes from.

As a way to objectively judge how useful a scan tool is likely to be, before you know the selection of problems you're going to end up encountering, it's more helpful to have a review thread that lists different scan tools and apps according to which ECUs in the car they are able to communicate with and give you trouble codes for. For gen 2, that would be the thread dolj linked to in #4 above.

I couldn't begin to estimate the number of threads I've participated on here where somebody had (usually) a brake, skid, or traction light, or an airbag light, etc., and only had Dr. Prius available, and so had to be pointed to the ➡blink codes method⬅ as the only way of promptly finding out what was up with their car.

That does work in a pinch, but only a subset of the ECUs in the car will give blink codes, and the subset gets smaller with every generation. It was a lot of the ECUs in gen 1, still a good number in gen 2, and maybe down to only brakes, TPMS, and airbags in gen 3. I'm not sure whether later generations give any blink codes at all.

Also, even when available, the blink codes are often strictly less information than a scan tool would give you. You don't get INF codes, and in some cases there is one blink code corresponding to several different DTCs.

I'll stick to the advice that, if you like having Dr. Prius around because of its distinctive, specialized screens focused on trying to monitor traction battery performance, by all means keep it around, but also plan to have another app handy that can show you the trouble codes for whatever goes wrong with your car.