2003 prius troubles

Your post is in the appropriate "Generation 1 Prius Discussion" forum now, so somehow you did post it in the right place, or a mod moved it for you. Anyway, right here is the place to be.

 

The name of the Toyota diagnostic software is Techstream. You might also be able to find other scan tools that will at least read you the trouble codes from the brake system.

But you can also get those without any scan tool at all. If you have a small piece of wire and bridge the Tc and CG terminals at the diagnostic connector, then turn the key to ON (no need to "start" or become ready), some of the dash lights start blinking. You can count blinks on the brake-related lights to get two-digit codes you can post here.

A little searching on the forum should find you some posts with more details on how that's done.

 

If you have that horrible alarm sound, you have brake system codes.

Forget whatever scan tool you are using, and get the codes by blink counting.

 

On the home page, go to "Forums" at the top, move over to "Prius," and when the drop-down menu appears, click on "1st Gen Prius."

 

Do you own or have owned toyoda Carina ? What country,?

 

Sounds like you must have found wrong instructions. Once you have placed the Tc to CG jumper and turned the key to ON, you should see multiple dash lights blinking. Even the ones that have no code to report will say so by doing a steady fast blink. (Also, if I remember right, a Gen 1 will switch the MFD to what looks like its usual infotainment diagnostic screens, only in Japanese. )

 

Had a Carina from Finland here in USA with the Beams engine and 6 spd . Great car.

 

There is a reference for them. It's in the repair manual. But (this is important), you need to say which codes were blinked on which dash light(s). There's a separate table for the codes that each dash light can blink, and some of the numbers are reused, so without knowing which table to look a code up in, you can decipher it wrong.

The bad news is ... if you didn't write down that information while you were reading those codes you just posted, you'll have to go do it again, and be sure to separate them out that way. But at least it will be familiar, and go faster.

I won't mind looking up a few codes in my copy of the manual ... but I will have to know which light(s).

 

Ok, well, we've got;

51 = C1251
52 = C1252
56 = C1256
64 = C1214

Looking at the first three, you could get the idea that the DTC for blink code xy is always C12xy, but that fourth one shows why you can't fool yourself that way. You just gotta look 'em up.

The C1251, C1252, and C1256 all have to do with the electric pump that forces brake fluid under pressure into an accumulator, to keep pressurized fluid always available for use when you brake. The braking ECU carefully monitors that electric pump, the voltage being supplied to it, and the current that it draws. There is an old post here with more details on how that's done.

The C1251 means that either one of these two things happened:

• The key was turned ON, and the pump motor drew more than 28 amps for more than 1 second, OR
• The pump ran three times in a row with its current draw changing by less than 7 amps during the run.

The C1252 means the braking ECU was trying to run the pump for more than 5 minutes without ever reaching the target fluid pressure. This probably means the pump wasn't really running at all.

The C1256 reports one of five possible problems with the brake fluid pressure switch (which is really two switches, one set for the low pressure where the pump should turn on, and one for the higher pressure where the pump should turn off). The five possibilities include various sanity checks (like, the ECU will set this code if the low and high switches are ever made at the same time), but the most likely possibility here is the third one, which is that the low-pressure switch was indicating too-low pressure for more than 60 seconds (as you'd expect, if the pump wasn't able to run and pump the pressure up).

The C1214 reports a hydraulic pressure problem, namely, that you had the brake pedal depressed and the several pressure sensors in the system were not reporting equal pressures, for 1 second or more. There are four pressure sensors in Gen 1, one for the master cylinder, one for the regulator, one for the front wheel-pair circuit, and one for the rear wheel-pair circuit. It makes sense you'd get this code if you have no pressure in the accumulator, because the master-cylinder sensor would still show pressure from your foot, but other sensor readings would be lower because of the lack of accumulator pressure.

So the problem most likely involves your pump and accumulator (though the smart money checks carefully for a wiring/connections/relays problem before just assuming the expensive parts need replacement).

The Gen 1 pump/accumulator assembly is buried over on the right side of the underhood space, at the firewall, near the engine; if you find the brake fluid reservoir and follow the tube down, you find it.

It's not easy to get to. There are A/C lines in the way, and the official Toyota procedure to replace it involves having your A/C refrigerant reclaimed so you can disconnect and move those lines, then replace the pump/accumulator, then have the A/C properly evacuated and recharged, all adding to the cost of the job.

There was a PriusChat member, rlin78, who wanted to avoid opening the A/C system, and worked out a way to do so. You can find his thread about it here. IIRC, it did involve some access from below, and possibly separating pump from bracket in situ before removal. The price of avoiding A/C evac and recharge seemed to be increased labor time on the removal and replacement, but if that can be DIY, it saves a bundle. Anyway, it's good to know it's possible.

Those are the same infotainment diagnostic screens you can get into with the tap-six-times Easter egg, except for the language being different. So if you're curious enough, you can go back to them the other way some time and see what they say in English, and then you'll know what they say in Japanese.

I don't emphasize those screens very much because they are really only built into the infotainment system for diagnosing itself; they don't tell you squat about the rest of the car*. People often stumble onto those screens and think "yippee, secret screens I can diagnose the car with!" and after the disappointment of learning they can't, they're never quite the same again, shells of their former selves.

* well, ok, the 12 volt battery measurement on the signal check screen is handy sometimes.