EMISS light and Code 41 stumped
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Freshman User
Joined: Dec 2002
Posts: 37
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From: New Bern, NC
EMISS light and Code 41 stumped
Was having hard to start cold or hot with an EGR code 33. Truck sits for a week or two in a cold garage -not used much lately. Fuel is a bit old too so I added a fuel injector treatment. Starting problem cleared by checking/remounting the EGR and replace the EVP sensor which was not in spec. Everything was OK, starting good, then after driving a few times EMISS light came on. Code is 41 during run test only (code 41r = lean, right?). In looking for a vacuum leak as possible cause I checked vacuum to EGR and found none, checked the EGR vacuum solenoid (EVR) and it would not pass vacuum to EGR so replaced it ($41 plus shipping & tax seems high for that part!). EMISS is still on and I can not find any vacuum leaks or anything else to explain it.
Any ideas. Appreciate your help, I'm stumped.
Also, will it hurt to run lean if that is what it really is doing?
Any ideas. Appreciate your help, I'm stumped.
Also, will it hurt to run lean if that is what it really is doing?
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Freshman User
Joined: Dec 2002
Posts: 37
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From: New Bern, NC
By cleaning do you mean to pull the sensor and use a solvent or brush to clean char from the sensor end? Is there a test for the sensor?
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
The EMISS light is operated by a timer and a timer only. The module is under the dash near the accelerator pedal, and can be either reset or unplugged. It is timed to come on every 80000 miles or so to get you to take the truck to the dealer and spend some money.
There really isn't any good way to clean an O2 sensor, but definitely do not use any kind of liquid solvent. The only test is to watch the voltage output from the sensor to see if it is switching between rich and lean like it should.
There really isn't any good way to clean an O2 sensor, but definitely do not use any kind of liquid solvent. The only test is to watch the voltage output from the sensor to see if it is switching between rich and lean like it should.
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Freshman User
Joined: Dec 2002
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From: New Bern, NC
EPNCSU2006 - thanks, I'll check/re-plug the module and let you know if that works. I was under there checking the cruise control brake vacuum swiitch a few weeks ago (unplug-replug the cruise module solved that mysterious problem, but that's another story...). I had no idea about the EMISS light as a maintenance check reminder timer only. IS that written up in more detail anywhere?
b-t-w - does NCSU refer to NC State? My son is an '07 grad.
b-t-w - does NCSU refer to NC State? My son is an '07 grad.
Thread Starter
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Freshman User
Joined: Dec 2002
Posts: 37
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From: New Bern, NC
That was a lot of effort and time for something that Ford could have made simple by putting an emission system check line litem in the maintenance schedule....Anyway, thank you EPNCSU2006 for pointing the way.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
Glad you got it figured out. I took my truck to the mechanic when the light came on, and when it came back I noticed something unplugged under the dash. I plugged it back in and the light was back on. I think I found the reset procedure in Chilton's manual, but ultimately ended up unplugging the module and moving the wire to the circuit for the Check Engine light so I could wire that to the computer output. I'm not sure why Ford didn't wire the CEL from the factory even though the dash had a spot for it.
NCSU is NC State...I also graduated in '07, a year longer than the 4 years I anticipated when I created the username.
NCSU is NC State...I also graduated in '07, a year longer than the 4 years I anticipated when I created the username.
