2005 4.4 - P0597 code

[Ashaman074]

Hello,

Over the last few years, occasionally I would get an error of P0597. Frequency could have been 1/year, possibly 2 - but it was a rare thing. I ordered a replacement to install at some point in the future.

Last month, the upper radiator hose burst, and i replaced it. I decided this would be an ideal time to go ahead and replace the thermostat while I was servicing the cooling system.

For about a week, all was well; but now I have a CONSTANT p0597 - the situation is not improved It is very frustrating.

I am not super-clear on how this circuit is supposed to function - I checked at the connection/harness with a volt meter and got a reading of ~8.0 volts with the key on - I have no idea what it should be, or if it is even a constant voltage. The connectors/harness don't appear to have any damage.

Now I am wondering if it is possible I got a defective thermostat. I cannot remember for the life of me where I bought it - and I hate to drain the system and replace it again just on the chance this might be the case.

Anybody have suggestions? Better yet, perhaps information on how this system is supposed to function or what readings I should see at the connector?

Of course, as chance would have it; I have to test/pass emissions next month; so this is less than ideal...

Thanks!