what causes a 2509 code
 

Ok thanks I will try two new batteries tomorrow

what causes a 2509 code
 

Ok I finally got some new batteries today but while driving it around my grid heater light keeps coming on what gives I have disconnected the wire to the selonoid from battery. What gives

Check for other codes. The grid heater is controlled by the ECM via the water temp sensor. Or it could be a faulty solenoid or a combination of both the solenoid and the temp sensor.

what causes a 2509 code
 

Well they supposedly replaced the temp sensor the day after I bought the truck and I know its reading right cause I've been running my scan tool and it's reading the same as the gauges.

How would I go about checking the grid heater solenoid