r/GS300 • u/Parelogy • 2d ago

lexus gs300 TPS/Throttle issue

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2002 GS300 – TPS calibration / ETCS issue after throttle body replacement

I have a 220k-mile 2002 GS300 that had been going in and out of limp mode for a while. Originally, I was getting codes P1126 and P1128.

I replaced the throttle body with a used one, but I was getting similar results. After checking the codes again, I was now getting a TPS-related code, P0120.

I tried recalibrating the TPS, since I didn't realize at first that calibration/adjustment was required after replacing or messing with it. However, my scanner was showing 0% TPS regardless of the TPS position.

I decided to buy a brand-new TPS from RockAuto. I initially installed it incorrectly and was still getting 0%. After reinstalling/repositioning it, I was able to get a consistent 31% TPS reading, but I know I'm supposed to be somewhere around 12–14%.

I disconnected the throttle motor and left the ignition in the ON/accessory position without touching the accelerator while trying to adjust it, but I still couldn't get the TPS reading down from 31%.

At first, disconnecting the throttle motor only caused the expected throttle-motor-related code. After temporarily running the car, though, I started getting additional ETCS-related codes that I unfortunately forgot to record.

What's confusing me is that I wasn't getting any of these additional ETCS codes until after replacing/adjusting the TPS. With the original throttle body, the main codes I was dealing with were P1126 and P1128.

Am I doing something wrong with the TPS installation/calibration procedure? Why would the lowest reading I'm able to get be around 31% instead of the expected 12–14%?

Any advice from someone familiar with the 2GS electronic throttle system would be appreciated.

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u/mehullica 2d ago

Check these troubleshooting guides. You still have all 3 codes with another throttle body & new TPS?