'96-F150,4.9L-5spd

My Ford has 138K on the clock. When I'm driving around town I have a check engine code illuminated. When I pull the codes I get a P0141. That code is consistent on day to day usage.

On the same vehicle, If I clear the codes before I drive in to the in-laws to deliver some goods, which is about 200 miles round trip. During that trip I get no check engine light. If I scan for codes when I get back, I get "0 Confirmed Trouble Codes" then after a few days of driving around town the Check engine light is back on. I scan and I get the same P0141. (02 sensor) I plan to change it, I think that is the sensor closest to the Catalytic Converter, but have not got to it yet.

But my question is why do I not have any codes on a longer trip, but the shorter trips throws a P0141?

Appreciate your help....

 

It probably needs a number of start/stops to confirm it wants to set a code.

 

The heater element in the H2O sensor is usually the problem. If it takes to long to warm up and communicate with the PCM that will trigger the CEL. It sounds like your description of what is happening is in line with this. Replacing it will probably improve your gas mileage some since the system will run rich until the sensor warms up and the PCM can apply the correct fuel air mixture. Sandy.