Temp gauge swings and code reader reads P0128

[giant h2]

I need some help. My 2005 H2 has been acting weird lately. The temp gauge sits on 160 when I knowthe engine is warm, intermittently shoots up to 210. The engine looses power (hesitates) and the trans shifts hard. Over the weekend I got a check eng light, scanned it and got a code of p0128. Cleared the code so far it has not come back however the gauge is sill all over the place and the engine and trans are surging. Any suggestions?