I have a 2003 2.3 DOHC engine that is idling rough and mil code P0597 states cruise control ckt open. This truck has no cruise control?????? Have replaced valve cover gasket ( due to leaks), intake manifold gasket (shop stated intake leak), both O2 sensors, pcv valve, plugs, ck'd all connections, and ck'd for vacuum leaks. When you first crank truck the RPM's start at 2000 and then bleeds off to rough idle. Seems to run fine going down the road, plenty of power but, stumbles bad when at idle. Any knowledge would be helpful at this point. Need check engine light gone to get emissions done to purchase tag. New to this forum but, lots of knowledge out here. Thanks

 

Welcome to the forum

Actually Ford P0597 means heated thermostat on the engine has no voltage or is unplugged or has failed

Check Fuse #41 in Engine fuse box, 20 amp, this powers the heater and several other devices

On the 2003 Ranger 2.3l Duratec engine the thermostat housing is on the engine end of the LOWER radiator hose, if its blown then there is a short some were, could be the heater but could be O2 sensor heater wires as well

This heater was not an uncommon failure, in 2004 Ford dropped it from this engine
Unfortunately you need to use the heated version, 3 times the price, unless you want to add a resistor so computer doesn't see an open circuit and set that code

 

Thanks RonD for the response. I will check the fuse out if that checks out I'll replace the thermostat.

Thanks again,
Rusty

 

man you hit the head on the NAIL with your response Ron D. thank you very much. 👌👍