2002 Prius waring lights

She really, really wants you to ask her why she is lighting the warning light (and to stop calling it "random", that really bugs her).

You can ask with a Mini VCI / VxDiag or by going to the dealer and letting them ask.

-Chap

 

You'll want to get the diagnostic code.
Then report back here.
That will help point us in the right direction as opposed to randomly guessing.

Some auto parts stores will read the code(s) at no charge. Else try a mechanic that works on Toyotas.

 

P0440 is simply an evaporative emission code. Often can be as simple as a loose gas cap.
P3191 can be kind of generic especially if the car needs a tune up in general.

Start with the tune up, clear the codes, and then see if they return.

If this is a car you plan on keeping for a while, at this age you may want to own your own set of diagnostic tools.

 

Yup, those make sense. The P3191 just means she's been having to crank the engine longer than she wanted to before getting it to start (keep in mind that can happen while driving, too, since the engine stops and restarts), and the P0440 refers to the evaporative emissions system, which involves a small clump of sensors and valves and vacuum hoses (and also needs the fuel tank to be leak-free). She only does evap system self-exams occasionally and under certain driving circumstances, so that's why you weren't sure of a pattern in when the light came on.

These days, a "tune up" really isn't a thing the way it was in the old days, when engines had a lot of parts with short lifetimes or needing regular adjustment, and instead of diagnosis, you'd basically just have a big day of putting in new stuff and redoing adjustments, and be running like a top again.

In a modern engine like the Prius, most of the parts have crazy long expected lifetimes, and it would be unnecessary and expensive to go replacing all the everythings just because some issue has developed somewhere. It's more effective now to do targeted diagnosis of the issue, then replace/fix whatever needs to be replaced/fixed, and call it a day. As you see from the codes, she can make it really easy for you to know where to start looking, if you just ask her.

I would definitely start by sleuthing out what's causing the P0440. There are a bunch of possible causes (the manual has a nice six-page procedure you can follow to pinpoint what caused it). One of the easiest ones to check is a loose fuel filler cap (when she does her self-exam, she needs to find the fuel tank airtight).

After that, there's another possibility I would definitely look at: Gen 1s have had a rust issue in the fuel filler neck itself where it passes above the rear wheel. The wheel kicks water (and winter salt) up in there, it sits on the steel filler neck and rusts it. She'll notice, with a P0440, because the tank's not airtight any more, but worse than that, the water kicked up by the wheel runs down in the tank and dilutes your fuel, giving you rough running and hard starting, which she has also mentioned.

People who have replaced the filler neck say it's not too hard.

-Chap

 

Regular OBD2 readers can scan but can't do a complete scan. A mini VCI uses Toyota software and will give you more complete scans and more information. Sounds like your experience level suggests that you should take it to a Toyota shop or a good Prius oriented hybrid independent shop and let them do the scans and investigation.

I've been doing my own work on my vehicles for almost (!) fifty years and you can cheat on oil changes and other maintenance. But as the old Fram Filter commercials used to say, "you can pay me now or you can pay me later." Good maintenance is the gift that keeps on giving.

 

The necessary codes were read in post #5.

I still think the filler neck would be a definite 'person of interest', if filler necks were people.

-Chap

 

I'll also vote on the filler neck. I found it very easy to do on mine.

Wait at your peril. Water in the tank does not a happy fuel pump make. It also leads to rust in the fuel line, which makes for injectors that weep fuel.

 

+2, Change Plugs, Air Filter and Gas Cap Oring, disconnect battery neg side then after all repairs, reconnect ( immobilizer reset ), turn key to on position ( do not start ) for 20-30 minutes, listen for water pump flow turbulence then turn off, remove the key and open and close the door. Start the car take her for a 20 minute drive.

 

Hmm, I'm pretty sure the 30-minute immobilizer reset is not something that is ever needed unless you have replaced either the HV ECU or immobilizer ECU....

-Chap

 

I stand corrected, I recall replacing the battery and did not have to reset.