I have a check engine light on my 98 LS400 with 87,000 miles. It acted like the tranny was slipping badly so I took it to a transmission shop and they said the tranny was fine but checked the light and it is code P1121 indicating the acelerator pedal positioning sensor needed to be checked. This will be done in 3 days. I have no idea what this replacement involves and would appreciate hearing from anyone who has some knowledge about this. Thanks

 

iirc the 98-00 is a drive-by-wire so the actual accelerator pedal sensor is dead/loose.

 

Thanks for the info.

 

I want to add that I have had to drive this car and the slipping problem is not continual. About 80% of the time, it shifts fine, Could this sensor have been knocked loose by someone doing a transmission fluid change? I had this done just before this problem started.