P0121

Hello. Wondering if anybody has dealt with this same issue.

I have P0121 engine code. I cleaned the throttle body, replaced TPS and this hasn’t been able to fix the issue. The pedal has to be floored to have any acceleration response.

 

Here are some of the possible reasons why you're getting this code: Faulty Throttle Position Sensor (built into Throttle Body Assembly), Throttle Position Sensor circuit is open or shorted, Throttle Position Sensor poor electrical connection, Faulty Engine Control Module (ECM). Since you already replaced the TPS (hopefully with OEM or Denso, these trucks do not like cheap aftermarket electronics), the first thing I would do is disconnect the negative battery terminal and let it sit for 30 or so minutes. This will reset the ECM. If that doesn't work, you're going to have to start hunting down wiring issues. Check the plug, check the grounds, check anything that looks remotely suspicious. I highly doubt your ECM is faulty, but anything is possible. I would suspect a wiring problem as the most likely scenario.

 

Go here: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

Note the links around paragraph 4 or 5. Get the FSM for your truck. Search for that code. Follow the instructions to diagnose/fix.

IIRC, the 2000 should be cable-driven, the "pedal has to be floored to have any response" makes me think you need to confirm tension on the line, but I've never touched an earlier-model V8 (assuming that's what you have, you left off that critical detail), so I'm not sure.

 

Thank you, all. Problem has been resolved. After inspecting all the wiring and numerous voltage and continuity checks, it was the TPS not getting any voltage due to the wire inside the pigtail connector not making contact with the terminal.

 

What he was describing was "limp mode", where the throttle pulley movement stops being a digital input, and starts being a mechanical influence on the throttle. I had mine apart for several days, while I learned.