the dreaded throttle control error codes

[FFRWRX]

This is going to be a bit of a long one. Do others have a bunch of codes that are always there and you just ignore?

This is a 2006 WRX drivetrain (drive by wire).

I've got these error codes, and the car starts/runs/drive fine (most of the time, which I'll get to):

P1518 – starter switch circuit low input
P0852 - Park/neutral switch input circuit high
P1152 - O2 sensor - but I did replace it
P1153 - O2 sensor - but I did replace it
P0113 - intake air temperature sensor 1 circuit high
P0502 - vehicle speed sensor A circuit low
P0503 - vehicle speed sensor A intermittent

BUT...I bought this 818C partially assembled by a previous owner, and I could see the gas pedal was replaced, so an indication that there might have been an issue. While working on the car, now and then when starting it the gas pedal would not respond. I would turn it off and back on and that generally cured it. Now the car is done and I'm driving it, it will go into a limp home mode now and then; won't go above 3,000 RPM. With the throttle floored it will go up to 3,000 RPM and then bounce there as if hitting a rev limiter. I would turn it off and back on, sometimes a number of times, and then it would be OK for the rest of the drive. The additional error codes were then:

P2127 - throttle/pedal position sensor/switch E circuit low
P2138 - throttle/pedal position sensor/switch D/E voltage correlation

I replaced the throttle pedal with a new one, cleaned all the connectors (throttle pedal, throttle body, throttle control relay, ECU) but it still occurred pretty much every drive. Yesterday it did it again on a drive, but wouldn't recover this time. Multiple times shutting it off and restarting and still would not go above 3,000 RPM. Checked the codes and the P2127 and P2138 were gone, but this new one was there:

P2122 - throttle/pedal position sensor/switch D circuit low

Cleared the codes and tried it again....no luck. So in a way it is good that it has gone from an intermittent issue to a full-time one. Intermittent issues are always a pain since you never know if you've solved it.

I removed the throttle body, cleaned it internally and the connectors again, but that didn't help.

I checked the real time data on my code reader and it showed the throttle position as: 14.1% at idle, 19.6% when floored

The factory service manual gives a lot of trouble-shooting but it is all to do with the harness. Is there a way to check the throttle body itself? Haven't found anything on-line. I have no issue with replacing it if that will solve this issue. But I really don't want to buy another one only to find that isn't the issue. New ones are of course very expensive, but there are "remanufactured/refurbished" ones on eBay for around $200.

I measured around 5 volts at three of the throttle body connector pins with the ignition on. The manual says it should be 10V, but I've also read that 5V is correct.

Any suggestions or help?

Rick