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?

[IRA51]

Probably a bad CTS or a bad conection to the CTS.

[giant h2]

my thoughts too where is the sensor?

[HumminNBoatin']

Could also be a Thermostat. I would start with changing both of them. Depending on your miles you might be due for new coolant as well.

Not really sure where the CTS is and my truck is not here so I cant just run outside and look for you. Usually its some where on the intake manifold. Should not be that hard to find.

[OrangeCrush]

Isn't 0128 the code that gets thrown when you've got a 160 degree thermostat in the truck? The reason it gets thrown is because the engine doesn't go into closed loop until 180 and with a 160 setup, it messes it up.

I know when I installed the supercharger on my last H2, I installed a 160. On COLD days if I started the truck up and drove, the CEL would come on.

If I let it warm up completely before driving, it wouldn't come on.

Unless I'm mistaken about 0128, there shouldn't be a misfire or problem coming from it.... just a light letting you know about the disagreeance between the computer and thermostat.

Mark