I'm getting the following codes:

P2122
P2138
P0643

Would this be a bad throttle body that needs replacing, the throttle position sensor or the acceleration pedal sensor? Basically it seems at higher operating temperatures the car goes into somewhat of a limp mode. I can't accelerate at all but the car still runs. When it cools down, I'm able to reset the codes and run the car normally.

 

not sure how you came to that conclusion that its any of those things, i dont have experience with the p0643 but that its sensor power supply, then it lists two sensors, that chance of two going bad at the exact same time is pretty much 0. you likely have a wiring issue or issue with the ipdm not sending power out, going to need to take it to a shop to diagnose.

also the proper place is maintenance not engine and drivetrain.

 

My apologies. If a mod can move the thread I'd appreciate it.

The TB being bad I came to that from a Nissan master tech that took a look at it with a scanner. I was thinking maybe it's a sensor because the other two codes are stating it's a sensor. All he did was read the code, reset it, and it's been doing fine, but I haven't driven in warm temps.

A couple other things that popped up (not codes) with Torque (app for my bluetooth scanner) were "Open loop due to insufficient temperature" and Open loop due to engine load or deceleration" as a Fuel System Status.

 

Another thing I should mention is I had my resonator replaced on the midpipe since it had a leak. Not sure if coincidental or because of what they did, but the muffler shop welded the resonator on while the vehicle was running. I thought you're not supposed to but apparently they do it all the time. I thought the issue arose originally because of that. Master tech said no it shouldn't and it's a coincidence but I've had other people (including mechanics) tell me you're not supposed to and it could have been the reason why it's acting up.

 

that means the 02's arnt heating up and we have heated 02's, also the decel is likely because its not reading anything else. you have several different sensors not getting power, its not the sensor its where they are getting power from

 

actually its very likely, welding is literally a short circuit, most times it will not go to other systems because the ground is so close but it is a very real possibility and if it does its going to fry anything it goes through, which in this case sounds like it could honestly be the ipdm, or heck one of several other things you need to take it to a actual shop its not going to be something you can fix or that we can diagnose over the net.

 

Yeah, blast from the past and my first post. Just trying to help some poor soul in the future who is desperately using Google to fix their car.

2006 350Z Base. Complaint: Car goes into limp mode immediately after warmup every time. Codes: P2122 APP SEN 1/CIR, P2138 APP SENSOR, P0643 SENSOR POWER/CIR, P0550 PW ST P SEN/CIR, P0452 EVAP SYS PRES SEN.
Following the FSM, codes P2122 and P0452 both refer to troubleshoot code P0643 first. I am lucky enough to have a graphing scanner and watched the signal voltages of APP SENSOR 1, EVAP PRESSURE SENS, PW ST Press sensor, and AC PRES SENS all drop to zero simultaneously. (Why the a/c pressure sensor? Because the FSM says it’s included in the circuit for P0643)
So I knew the computer was probably good and reacting to a high or low signal voltage from one of the input sensors and killing power to all the sensors. My method of T/S was to install a backprobe into ECU terminal 48 (evap power supply, but it could have been any power supply terminal to a sensor in the P0643 diagnostic) with a T Pin and then reinstall the connector back on to the ecu. Then install a meter set to volts from T PIN to ground. That way I could watch the reference voltage(not the signal voltage the scanner sees). Start the car up and induce the limp mode.
Without going into theory of operation, I’ll just say start disconnecting sensors at the most suspicious spot while the car is running and limp mode is induced. You are looking for the reference voltage to jump back to 5v.
I disconnected the power steering pressure switch first figuring it got hot the fastest. (Use a pair of hose pliers with the circle pincers. It’s almost impossible to disconnect by hand.)No luck. I left it disconnected. I had the bumper cover off anyway, so I disconnected the ac pressure switch next and ta-da! Voltage came back to 5v! I left it disconnected and shut off the car, waited 10 seconds and started it back up. Limp mode gone! Reconnected the ac pressure switch and it immediately went into limp mode. Faulty sensor identified. Parts on order.
WARNING: disconnect battery negative cable before disconnecting or reconnecting the ecu. Same with any super multiple junction connectors. Also DO NOT probe the front side of any connector. You WILL deform the pin and induce more problems. Go to a beauty supply place and ask for T-Pins. I think they use them to pin wigs in place.
If you searched this post out. You are obviously screwed. Get a digital copy of the factory service manual. Read up. Find all your sensors and connectors. Be patient. You can do it. (Correction: if you can’t use and understand a multimeter, throw away your tools and take your car to a shop.)