My 2000 Saturn LW2 starts hard shifting after city driving about 16 kms. If I turn the engine off for one minute and start the car the hard shifting stops and I can drive another 10 kms before the hard shifting starts again.

It threw the codes P0405 and P0030 Bank 1 Sensor 1. I changed the EGR the P0405 code (Exhaust Gas Recirculation Sensor) and the trouble light continued to come on and the hard shifting continued after about 16 kms.

I changed the Oxygen Sensor the P0030 and the trouble light still comes on after 16 kms however now if I 'rapid' accelerate the trouble light comes on a bit sooner and hard shifting returns.

The only thing I can think of is that the Saturn requires an OEM Oxygen Sensor and not an After Market Oxygen Sensor? Or the heat of the engine has damaged the wiring harness? Anyone have a solution to fix this and stop the hard shifting?

 

Welcome, your car has three problems not just two. Two may be related to the ecm. I will post a link to factory diagnostic manuals. The transmission hard shift turns on the wrench light not the check engine light. The wrench light indicates a problem that is not emission related. The force motor inside the transmission is the usual cause of this. My first LW300 had this transmission problem. I chose to not repair the transmission issue since it was just a commuter car for me. If I drove the car without spirited acceleration the problem would rarely occur.

 

I won’t be any help with this, sorry.

 

Always use OEM sensors. Do that and see what you get.
If you have tools and know how to use a manual there's this.
https://charm.li/Saturn/2000/LW2%20V6-3.0L%20VIN%20R/

 

Andy and Gary are both lifelong mechanics.
I believe Andy has resurrected 10 to 15 L Series vehicles during the time he has been on this forum. He has rebuilt the engines and rebuilt the transmissions as needed. His response sounds to me like he has already performed troubleshooting for a similar situation. At least far enough to decide not to pursue it further as his needs did not dictate that he do so.

Every situation is different, but both Andy and Gary's track records are pretty hard to beat around here, not that anyone's bothering to count. I strongly urge you to consider his feedback as you attempt to address your issues.