My in-law's 2004 grand is showing 3 codes. I already did some searching and found the following:

P0051 HO2S Heater Circuit Low Voltage Bank 2 Sensor 1

P0121 Throttle Position Sensor Circuit Insufficient Activity

P0152 HO2S Circuit High Voltage Bank 2 Sensor 1

My question is, how are they related and what is my first step in troubleshooting/repairing? Thanks

ill go to the shop today and look in our database and see what i can find for you

Thanks Trapper but I already fixed it. My father-in-law told me to just go ahead and replace the O2 sensor in question and the TPS since it has 100k on it. I picked up the two parts from the dealership this a.m and had them swapped out pretty quick. She runs and drives WAY better than it did and I haven't had any codes pop back up.

I'd start with the O2s as well.

http://www.rockauto.com/catalog/raframecatalog.php