I just had my 97 F 150 with a 5.4 in to the dealer for the check engine light. They said it was the O2 sensor, in front of the cat on the right bank. Had a Bosch sensor put in and two days later the ligh is on again. Any ideas out there? Would a bad fuel filter cause this? It did begin to idle rough while at a stop light. It also only has 24,000 miles on it. Could it be that once one O2 sensor goes, they all go( hope not )? I am puzzled!

 

Get the code read at an Autozone and then comeback and post what the code came up as. It's very rare that a O2 sensor will be the culprit. I recently had a CEL come on and it turned out to be the rubber elbow at the end of the PCV valve hose that goes in to the manifold. Start your engine up and feel in the back where the hose connects up at. If you can feel a vacuum sucking your finger then that is your culprit. Definitely get the code read though, as this will at least start you off in the right direction.

 

I have the same problem. I'm going to Autozone in the morning and see what I find out.

Joe

 

I have learned to just ignore mine..
It comes on and stays on for a while and then goes off. My stepdad who is a mechanic for MODOT said it is probably the charcoal canister on the gas tank plugged up. My truck never behaves any differently when the light is on or off (it mostly just pings all the time!)

 

I went in to auto zone and the diagnostic code was P0401 which indicated a faulty EGR. I didnt purchase it because I wanted a closer inspection. I found a cracked coupler that joins 3 vacume hoses next to the battery against the firewall. One of which goes to the EGR. After I replaced the broken coupler I reset the CPU to clear the inidcator and so far it has not come back on. All it turned out to be is a simple vacume leak.