Anyone here encountered the P2121 code with the Sprint Booster? Had one installed for about 2 yrs with no issues until 2 wks ago when I got the code which caused the limp mode performance. Cleared code, removed/reinstalled SB and all was well until yesterday when problem repeated itself. I cleared the code & removed SB. I reached out to Jason yesterday asking if that was a sign of the SB reaching the end of its life cycle & he responded no. He asked if the light on the controller was on and I replied yes.
Never heard back. Not reinstalling it for a month to see if the problem is being caused by the SB or if the APP sensor is the problem. Looked at wiring & connector which seemed fine. I read where someone with the PC had same problem and it was the PC.

I don't have any codes, but mine is acting up right now. Floor it and it won't accelerate. I can slow down some and it will start working again. I am going to reconnect the factory plug and see if everything is ok which would mean it was something to do with the Sprint Booster.

Well, this may postpone my purchase.

I removed mine and sold it. Did not want to deal with issues like this.

It sounds like @mteolus has a failing unit. And probably @TRDfan2011 also. @Jason B guarantees the Sprint Booster for 5 years. He and the manufacturer would probably be interested determining the failure mechanism. Please let us know what the resolution is .

I reached out to Jason on 7/9 to see if he could shed some light but he never responded to me after I answered that the controller light was on when problem presented itself.
It would be nice if SB had "self turnoff" when it encountered
a problem so that it would be automatically bypassed and not leave you in limp while driving in the mountains. Now I'm also wondering if the SB is beating up the APP sensor.
I don't want to start speculating but I'll wait a month to see if code returns. It's all part of the modding experience. The ball is in Jason's court. Don't know if he's looking into the issue and he just forgot to tell me but I'll let it be.

Subscribed. Interested in the outcome on this and the cause of the issue.

Any chance you know any other 4Runner owner that is located near you that has a Sprint Booster? Maybe you can borrow theirs to see if the problem continues?

I don't want to experiment and risk creating a big problem. I currently have it removed and will wait 30 days to see if problem was caused by SB. I was hoping that Jason would have provided some technical insight but he did not. Could be possible that SB has nothing to do with the CEL. Bottom line is that I will never use SB again. Too many unknowns to risk creating a bigger expensive repair.

You’re doing the proper thing now to get a baseline to see if the problem reoccurs. The Accelerator Pedal Position sensor is incorporated into the plastic module of the pedal. From what I can tell it’s simply a redundant transducer, or potentiometer, that outputs two signals to the Engine Control Module. The ECM compares the two signals and if there’s any difference between them the ECM determines its a possible pedal problem and puts the vehicle into limp mode as a safety feature. Auto manufacturers don’t want a pedal failure causing uncontrollable wide open throttle.

The Sprint Booster is plugged in between the APP and the ECM and merely amplifies the output signal so it reaches full scale output sooner. All electronic devices can fail, so it is possible the SB has an intermittent or noisy output that doesn’t match the other one occasionally and the ECM doesn’t like it.

This brings up another question that I haven’t been able to figure out. Does the Sprint Booster maintain the two independent pedal output signals to the ECM, with separate circuitry, so it can do it’s safety checking? Or does the SB merely send the same signal out on two separate wires to fool the ECM? @Jason B should be able get this answered.

Ost.

I wonder how hard it would be to modify things so you can get an old school cable for the throttle body.

Maybe try resetting the ECU? disconnect the battery for 10min and see if that fixes things?

I have a scanner and cleared the code both times. The scanner is now stored in the glove box. It's painful driving the 4runner with the CEL cause it goes into limp mode.

I wonder if it has anything to do with the extreme heat? Mine sits outside on the driveway and it has been 100+ degrees. Otherwise here is the issue I am having. Slowly depress the pedal and it seems to work. If you press the pedal fast it stops accelerating all together. So if I am going 50 and punch it, it stays at 50, same thing if I were going 70.

This happened a couple of times last year but started working again.

I disconnected it back to factory and works fine. I guess I'll flip a coin and see if I can get a replacement on warranty. Mine is almost exactly a year old so it did go through part of the summer last year in heat.

https://www.toyota-4runner.org/3473183-post225.html