I'm trying to get an inspection sticker and the following codes keep coming up, P0443, P0141, P0155, P0135. We know that 3 are bad o2 sensor codes, we replaced all O2 sensors, the distributor, all 8 plugs and wires, the catalytic converter has been tested, replaced the fuel filter, clean air filter, and changed the oil. Also replaced the rear fuel tank and fuel filter. We've checked all the fuses and the wiring and connections of the emissions system, no issues found. We took the intake canister for the emissions center apart, cleaned and reinstalled it, adjusted the timing.On several occasions we've unhooked the battery for 24 hours and drove it for 60 miles each time to reset. Out of ideas... any help would be appreciated.

 

You have codes for all 3 O2 heater circuits which means a blown fuse or a chewed wire, start with the fuses and if that checks out OK you're gonna have to trace the wires all the way back to the computer.

 

Any idea which fuse? We have looked at all the fuses and they seem to be ok but we can't find info anywhere on which fuse we are specifically looking for. Thanks

 

Have you got an owners manual for that truck? Fuse diagrams should be in there.

 

you only have 1 cat on there? I thought there were 2? I had this problem myself and I put a CEL eliminator on the front o2 sensor cleared the engine light and code and tested it...passed with flying colors.

 

For what it is worth. I didn't have a light on my 95 F150 OBD I system but if you go up by the battery there is a wire that involves the 02 sensor. Mine was corroded & was causing a low trim reading. So you might check that.

Craig

 

Problem is you essentially disabled the EFI system.. may as well put a carb on it.

 

I have run across a few instances of the dreaded P0443 and other codes that seemed unrelated: Ford Truck Enthusiasts Forums - Search Results

The O2 heaters are fed from the PCM fuse via the PCM relay. The returns are all controlled via the PCM on different pins. I do not see a common tie point other than the PCM fuse/relay and PCM itself.

 

Well if I disabled the EFI then I'm a lot happier because I get 4 mpg more than I was. Besides that all you're doing with a CEL eliminator is you're moving the o2 sensor out of the main stream by about 2 inches is all. If the cat is running low efficiency the PCM / ECM tells the fuel pump to pump more fuel which means less MPG, Move the o2 out of the main stream and it reads different, then the PCM / ECM readjusts for that difference and tells the fuel pump to back off and not pump so much. So you're not disabling the EFI, You're just get the computer to do what you want it to do.