I have a check engine light and Pulled P1121 and P0121 error codes.

Those are TPS sensor codes basically a voltage issue what happens when you drive the car? Does it drive park drive away when you're ready then I would say yeah you can drive it until you can't if the voltage spikes and ruins the TPS or any of that goes on then the car may or may not run may run in a limp home mode only to get you home so on and so forth me personally I'd be driving the car till I wasn't or I'd hop on my Aprilia scooter or any other of the five vehicles here but generally I would drive the Prius I'm driving one right now with the Christmas tree lit up and at random literally almost no brakes but you never have no brakes and a Prius you may have limited. So I would say drive on You should be getting to fix it probably before it completely stops working.

 

i haven't used them, but there is a lot of chatter here about bad counterfeit parts from non dealers

 

Your best bet and what I found is my best bet is when I'm out at LKQ I take three or four of these things and just keep them in my box and then I put them in my spare parts at the house some of these TPS sensors and mass air flow sensors and that sort of nonsense can get quite expensive actually One of the mass air flow sensors on a Toyota I recently worked on was $189 I took one from another car at LKQ so I wouldn't have to buy a counterfeit so the person wouldn't be worried about spending $200 on a brand new Toyota part for a 19-year-old car so on and so forth plugged it up cleaned it plugged it up working great Guy couldn't be happier so there's always that If you're in it for the long haul and you're keeping the car and there's no ifs ands or butts then by all means spend the cash money and buy the original part if moved to do so.

 

I just replaced my coolant control valve. it was about $125 at the dealer for a Toyota part. Mine failed in a position where there was no heat in the car, but the car itself was not overheating. Also there was no coolant being put in the thermal tank, but I didn't care much about that.

Had a Prius years ago, that the only symptom of a failed control valve was storing and retrieving coolant from the tank and I let it go for over a year, until ultimately I had to replace it to clear the CEL and pass NJ inspection.

Don't buy aftermarket. My current prius had a failed Dorman unit. Seller installed it less than two years prior.

Cleaning the throttle body is a maintenance item. Its not too much work and you just need to get at it with spray cleaner. Its on my list of things to do. The only thing it cost me last time was a throttle body gasket and some throttle body spray cleaner. I did lift the throttle body and put a small plastic tray under it to keep the muck from washing down. Hopefully cleaning that might free up any binding that can cause a bad throttle position reading. Just a thought on that.

 

P0121 is indeed about the signals coming to the ECM from the throttle valve position sensor on the throttle body.

The sensor is really two independent sensors, and two voltages come back to the ECM, called VTA1 and VTA2.

This picture is from a Gen 3 repair manual (pic was already uploaded), but the Gen 2 details are not much different:



The important thing to see there is that VTA1 and VTA2 are not identical voltages. VTA2 is always a bit more than a volt higher than VTA1, and the slope of VTA2 is steeper.

(The picture showing magnets and Hall sensor ICs only is right for Gen 3. The Gen 2 sensor uses potentiometers. But it works the same, in that the two voltages have an offset and different slopes.)

The ECM is always watching both voltages to make sure that they both are in range, and that they both have the right relationship to each other; any one of those checks not passing would mean something is wrong with the throttle sensor or the wiring. There are eight different trouble codes you can get, indicating just what check wasn't right.

The P0121 code indicates a basic problem with the relationship between VTA1 and VTA2; it means the difference (VTA2 − VTA1) was smaller than 0.8 V or larger than 1.6 V, neither of which should ever happen.

The code is pretty specific for the throttle position sensor itself, because some problem in, say, the wiring, would probably have shown up as one of the other P012x codes that are based on simpler checks. A 2006 repair manual pretty much says for P0121 to go right to replacing the throttle body.

 

I don't think Toyota will sell you the sensor except already attached and calibrated to a throttle body, or allow one of their dealers to try that. That might not mean you can't try yourself, if you find the sensor somewhere.

 

Should be plug and play, yes.

 

Odd that the sensors aren't sold separately. Are they mounted in some peculiar way that would have made replacement difficult?

In this thread:

throttle position sensor | PriusChat

there is a post that said cleaning the throttle body fixed the sensor problem on one car.