Airbox missing bottom gasket. Long term consequences?

I can't say that I remember such a gasket. You're sure it doesn't just cinch down on the top of the throttle body with a worm-drive clamp?

What was the connection between your throttle body/MAF sensor and the P1121 cooling system code?

 

Edit: posts crossed. If it was really P0171 all along, then the info below isn't needed, but I'll leave it because it shows how in fact P1121 can appear to mean throttle body or MAF sensor for other cars, not the Prius.

A P0171 is a lean-mixture code, and if in fact there's supposed to be a gasket down there and there isn't, air entering the intake at that point, beyond where the MAF sensor can measure it, would be one of the classic causes of a P0171.

Got it. What you did was you looked up P1121 in generic trouble code sites on the internet.

The trouble is, all P1 codes are defined by car manufacturers, not by SAE, so the same P1xxx code can mean completely different things from one make or even model to another.



As you can see from this page here, even Toyota has used P1121 to mean different things in different cars.

Code:

    P1121 ACURA Throttle Position Lower Than Expected
    P1121 AUDI HO2S Sensor Heater Circuit Short To Ground Bank 2 Sensor 2
    P1121 BMW Pedal Position 1 Range/Performance Problem
    P1121 BUICK Throttle Position Sensor Circuit Intermittent High Voltage
    P1121 CADILLAC Throttle Position Sensor Circuit Intermittent High Voltage
    P1121 CHEVROLET Throttle Position Sensor Circuit Intermittent High Voltage
    P1121 DODGE Decreased Engine Performance Due To High Intake Air Temp
    P1121 FORD Throttle Position Sensor Inconsistent with Mass Air Flow Sensor
    P1121 GMC Throttle Position Sensor Circuit Intermittent High Voltage
    P1121 HONDA Throttle Position Lower Than Expected
    P1121 HYUNDAI Throttle Position Input - Abnormal
    P1121 INFINITI Electric Throttle Control Actuator
    P1121 ISUZU Throttle Position Sensor Circuit Lower Than Expected
    P1121 KIA Throttle Position Sensor Signal Invalid
    P1121 LAND-ROVER Accelerator Pedal Position Sensor Range/ Performance Problem
    P1121 LEXUS Accelerator Pedal Position Sensor Range/Performance Problem
    P1121 LEXUS-2 Coolant Flow Control Valve Position Sensor Circuit Stuck
    P1121 LINCOLN Throttle Position Sensor Inconsistent with Mass Air Flow Sensor
    P1121 MAZDA Throttle Position Sensor Inconsistent with Mass Air Flow Sensor
    P1121 MERCURY Throttle Position Sensor Inconsistent with Mass Air Flow Sensor
    P1121 MINI Pedal Position 1 Range/Performance Problem
    P1121 NISSAN Electric Throttle Control Actuator
    P1121 PONTIAC Throttle Position Sensor Circuit Intermittent High Voltage
    P1121 SATURN Throttle Position Sensor Circuit Intermittent High Voltage
    P1121 SUBARU Neutral Position Switch Circuit
    P1121 SUZUKI Throttle Position Sensor Intermittent High Voltage
    P1121 TOYOTA Accelerator Pedal Position Sensor Range/Performance Problem
    P1121 TOYOTA-2 Coolant Flow Control Valve Position Sensor Circuit Stuck
    P1121 VOLKSWAGEN HO2S Sensor Heater Circuit Short To Ground Bank 2 Sensor 2

The "toyota-2" meaning, about the coolant flow control valve, is the only thing P1121 means in a Prius.

If it hasn't come back for a month since you cleaned the throttle body and MAF sensor, then you have a nice clean throttle body and MAF sensor, and your coolant valve hasn't acted up this month, but they're not connected.

This is the main reason why doing generic searches for trouble codes on the internet can often lead you into a bunch of wasted time, and the repair manual for the car (more info) is the most sensible place to look. Certainly for the manufacturer-defined codes.

If you're looking up a standardized code (one in the SAE-defined P0, C0, B0, or U0 ranges), then a generic internet search is less of a gamble. But you'll still get more directly useful information by looking it up in the manual.

 

I wasn't there for the search you did, but P1121 in a Prius refers strictly and only to the Gen 2 coolant flow control valve. The listed trouble areas are that valve itself, clogging of the cooling system, or a faulty ECM, full stop. (And that last one is just to cover the case where you find there's absolutely no problem with the valve or the cooling system, and some failure in the ECM must be causing the code; pretty much not a thing that happens, only the list would be logically incomplete without it. ) They didn't list the coolant valve/sensor wiring, but of course that's part of the circuit too.

If you found a source that said there were "other possible causes" in a Prius Gen 2, then you found a source where somebody else had made the mistake of looking up a P1 code in the wrong places. That kind of thing happens too. It can be surprisingly difficult to put things like that to rest.

I think I do remember that thing now that you describe it further. Sort of the stuff of door weatherstrips. And I agree, I don't see it offered as a separate part, not in figure 17-03 and not in figure 22-11. That's kind of frustrating.

You could almost make the thing out of some door weatherstrip stuff, except for how to join the ends.

With it missing, I would be expecting pretty much classic symptoms of unmetered air, including lean mixture drivability issues and P0171 codes.

Maybe three or four wide rubberbands? I sometimes get some good ones on broccoli.

 

Does that mean you found a "hybrid mechanic" who believed P1121 had "possible causes" other than the coolant control valve and sensor, in a Prius? Funnier things have happened....

$18 is a good price. Less fuss than gluing up door weatherstrip.