I have an 2005 V10 3valve 126k miles with what I think is a lean condition. I am getting P0141,P0161, bank 1&2 sensor 2 heater circuit codes, (same sensor) and also P2195 and P2197 bank 1 sensor 1 and bank 2 sensor 2 lean codes. The heater circuit on sensor 2 checks out good. New motorcraft air filter, new wix fuel filter, 10 new motorcraft spark plugs, oil just changed, throttle body and MAF sensor cleaned. No misfires present. Also spent hours looking for a vacuum leak with no success. truck runs good under pedal but does not idle well. when its at idle it sounds like it has an aftermarket cam set up and the exhaust has an awful rich smell to it. So I believe the O2 sensors are telling the PCM the truck is running lean therefore causing the truck to dump more fuel and in turn causing a rich condition. Cannot access PCV Valve as it seems Ford incorporated them into the valve cover. Beyond frustrated at this point. Any Ideas?? Thanks.

 

Sure sounds like a vacuum leak to me. It is very hard to check the rubber hoses for cracks while they are still on the truck. I would start removing them one by one and doing a detailed check. It doesn't take much of a crack for vacuum leaks.

 

I have removed the hose from the purge valve to the side of the throttle body and the hose from the passenger side valve cover to the air intake tube and inspected both and found no cracks. I also plugged these two hose connections (one at a time) at the intake to be sure it was neither of these hoses.

 

There is almost no way a heater circuit code can be logged, and not have a heater circuit issue. When you say it checks out good, how did you test it? Right at the O2 sensor connector, or all the way back to the PCM?

My '97 Cougar one day started to log heater circuit codes. Everything checked out good. And I do mean everything, all the way back to the PCM. PCM had to be replaced. Not saying yours is bad, but you really need to check it all the way back to the PCM.

The way it's acting, you're right, the PCM thinks it's lean, so it's fattening it up as much as possible and going full rich.

Check battery voltage, grounds, etc, before everything else, just to make sure there's nothing obvious there. A bad diode in the alternator can make the electronics go nuts. If and when it idles smooth, do the lights (headlights, etc) flicker?

After that, you really need to dig further - datalogging the O2 sensor voltages would be the first thing.

 

I checked for continuity through the heater circuit on the O2 sensor itself and I used a test light and had power through the vehicle harness. I will revisit that vehicle harness with a volt meter to get a more accurate reading. What you say makes sense. The P0141 and P0161 codes have been a concern to me. Could that O2 sensor heater circuit confuse the upstream O2 sensors? How many volts should I have on that downstream O2 Sensor heater circuit? Probably wont get back to diagnosing until Thursday as we are preparing for snow coming in tomorrow into Wednesday. I will have to get a pin diagram of the PCM somewhere. Thank you.

Also, no flickering of lights anywhere or other issues except for the common trailer brake control alarm going off periodically, I'll have to address that after its running right.

 

Got back to this truck issue today, key on, engine off, I have continuity from PCM plug to O2 sensor plug on heater circuit wire. Checked for voltage output on corresponding pin on PCM module and was only getting 1 volt at best. I believe I should have 5 volts there. Is it time to condemn the PCM or are there any power input or grounds I should be testing at the PCM first?

 

Measuring output from the PCM is tricky - I'm not sure the PCM turns on the heater circuits right away. And of course, the engine has to be running. I'm going by the '97 Cougar I talked about before, BTW - not sure what the newer OBD-II stuff does. I'd monitor the voltage from the PCM for a few minutes as the engine starts to warm up.