2003 Prius Runs perfect, then shuts down

Those are good lessons. If you're going to be keeping a Gen 1 running, you might also want to have ways of reading the codes yourself.

I'm surprised that any mechanic would have looked at an "Inverter Malfunction" code and told you what the car needs is a transmission. I wonder if he thought of the inverter? I also wonder if he (or you) checked for the fluid-level step in the inverter coolant bottle that proves the pump is working when the ignition is ON. That's a simple thing to check, and the pump's not very expensive if it has given up the ghost.

In any case, what really matters when you read a code is not the one-liner fortune cookie description built into the scan tool or somebody's cheat sheet, it's the information in the repair manual that goes with that code. In the case of a P3125 in Gen 1, it turns out there are additional detailed "INF codes" that can also be read along with the main code. There are 81 of these possible with a P3125. There are 36 pages in the Gen 1 repair manual on the procedure for pinpointing the cause of a P3125. (This is where the INF code can help, because it lets you jump in at a known place in those 36 pages.)

If the mechanic has given you any "oh, it must be this" conclusion without going through that diagnosis (especially if it's an odd conclusion, like new transmission for an inverter code), it's probably worth a deeper look, especially as the true cause could turn out to be something less expensive.

-Chap

 

Actually, it sounds like he may be right on it. Luscious Garage posted this in their blog Gen 1 Prius Transmission Repair, P3009, P3120, P3125 - Luscious Garage | Hybrid Specialists It could be the MG2, which is the alternator and the left side electric motor.and, depending on your adventurousness, is something you could tackle. I know where there are about 4 of these in junk yards in Tucson & Phoenix. You might try the local "u pull" style jy's in your area. Something in Omaha, Council Bluffs, Lincoln, or even Des Moines?

I find that having to take them out in a JY is good practice for putting them in your car. Almost worth the price of admission.

Btw, I've thought of stock piling some of these. I think the local Pick a Part or whatever might sell them as alternators, which would price them at about $20. Summer heat is the only thing keeping me from spending a day pulling them..

 

Check to make sure your inverter pump is functioning. Key on, remove cap and you should see liquid flowing. Key off, no liquid movement.

 

Carolyn Coquillette is awesome, and when she puts these details into a blog post, I would take careful note:

If I'm reading the original post right, and no info codes have been posted yet, here's about where this diagnosis now stands:

☐ Shudder during takeoff
☐ Louder whine during regen braking
☐ Red thermometer
☑ Master warning light
DTCs:
☐ P3009
☑ P3125 (?) inf 287 (info codes not posted, a 287 would be one out of 81 different possibilities)
☐ P3120

Two out of seven of the gross observations and a 1 in 81 chance on the inf code that hasn't been posted is not yet "he may be right on it" territory for me. For the immediate future, I'd say time would be better spent reading that inf code and checking the inverter coolant circulation than rushing to buy a stator.

-Chap

 

About 7 years ago, vincent1449p figured out how to query the computers for a bunch of things, including the INF codes; there's a big thread about using the ScanGauge II with the '03 Prius, where the SGII is a thing you can buy in the PriusChat shop that is mostly for displaying some extra gauges while you drive, but you can enter extra codes into it and have it query for those. The same info was also ported over for use with the Torque app that runs on a phone. If you have hackerish tendencies, you should be able to use the same information with about anything using an ELM327 chip.

The easy way is if you have a sort of burner laptop, a cheap J2534 cable and Toyota Techstream, which you'll find a lot of threads here about.

Most of the computers do keep historical codes for some period of time. If you're using Techstream, sometimes you can see a "freeze frame" with a given code, where a lot of other information was saved at the instant the code was set. So you could try looking for historical codes, and if you find them, great, and if you don't, then you just wait for the next occurrence.

I would definitely put thoughts of a stator way to the back of my mind for now, unless/until more codes read or info comes in all pointing to that out of the multitude of other possibilities.

-Chap

 

Odometer reading?

My advice is that the OP needs to get Mini VCI so that he can determine the DTC without reliance on someone who has a financial interest in influencing the information provided to the OP.

I also suggest that the OP should do some of the basics, like replace the iridium spark plugs if that has not been done in the last 60K miles, and clean the throttle body interior and throttle plate. Make sure the engine air filter is clean. Then see if the issue continues to come back.

Also, make the Prius READY and look for fluid turbulence in the inverter coolant reservoir. If this cannot be seen then the inverter coolant pump has failed.

 

The Classic Prius is known for having an engine low-power or no-start issue associated with the throttle body building up deposits. I personally experienced this with my 2001 many years ago when visiting Palm Springs in hot summer weather.

When you try to start the engine - just because you see/hear the engine spinning, that does not mean the engine is actually running. It could just be MG1 spinning the engine trying to get it to start. Proof of whether the engine is actually running is that you can depress the accelerator pedal and the engine speeds up.

The cosmetic appearance of the car has very little to do with its actual powertrain performance.

Hence I suggest that you ensure the car is current on its scheduled maintenance before you look for an obscure and costly root cause.

 

so, was the throttle body guilty? End of story?