Last week the check engine light came on so I looked and it said "throttle position sensor" P0120. I proceeded to replace it but that did not fix the problem. I continued to replace the ECM and the problem was solved. However, the transmission is now shifting very hard. This started when the TPS went bad. What should I do to fix it?
For many vehicles, regardless of manufacturer, there is the need to do a "re-learn" sequence (after replacing the TPS or a battery) so the TPS and transmission will work smoothly. You may have to drive the vehicle for a bit in order this re-learning procedure to complete. If you are still having problems after a couple of weeks, I recommend having a professional mechanic inspect the shifting issue and check the TPS and transmission for proper operation.