P0171 p0174 codes please help

[Bedrck47]

Being you say it happens when the temp drops below freezing I will take a guess which I normally don't like to do. But the only thing I see that is affected by temperatures in the intake system would be the INTAKE AIR TEMP SENSOR and the MAF sensor. It could be possible that when the outside temps drop to below freezing that the sensor could be opening up and giving a false reading to the PCM

 

[Bedrck47]

Intake Air Temperature Sensor
The intake air temperature (IAT) sensors (Figure 33) and integrated MAF type (Figure 36), are thermistor devices in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.
Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.
The IAT provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the calculation of fuel, spark and MAF.
The IAT sensor provides a quicker temperature change response time than the ECT or CHT sensor.

Being you have cleaned the MAF sensor try cleaning the IAT sensor

 

[Jiggers]

Can you access the IAT reading with your scan tool?(intake air temp) It is may be part of the MAF sensor or in-line in the intake tube , and if not reading correctly can cause the pcm to lean the fuel trims out causing your issue. Also I would suggest running some type of fuel treatment ,(I use Lucas), because the amount of ethanol in the fuel now-a-days can cause issues with 02 sensor readings also. A vacuum hose sucking closed can cause those codes also, or a stuck closed pcv valve.

 

[csdangerous]

I have that issue with my 01. I did actually need to replace my EGR valve to clear my CEL, and now I only get one intermittently on cold mornings. It reads p0171 and p0174 everytime. I bought a BAFX scan tool from Amazon, and a paid Torque Pro app from Google Play, (BEST 25 DOLLARS EVER SPENT !) so I plug in, clear my code, and it doesn't come back until some other random cold morning. Definitely going to change the fuel filter tho, just because, as I have no idea when or if it's ever been changed in it's 156k mile life. Cold air must be kryptonite for Ford systems...

 

[Insane451]

Ok so here's an update on what's going on with my truck. A couple days ago it got way below freezing again and the check engine light came back on same codes so I disconected the battery to clear the code and that night (still below freezing) it came back on on my way home from work. So that pretty much confirms my theory that it is some how due to the weather and possibly the air charge temp sensor (same thing as intake air temp sensor) so today I replaced that. It is below freezing today and tomorrow so I will see if the check engine light comes back on in the next day or two if it doesn't I hope the air charge temp sensor was the fix. If the check engine light comes back on I think I might replace the mass air flow sensor.

 

[Bedrck47]

Keep us posted to the results Thanks

 

[ukrboy]

Have the same problem. Went skiing on Sunday and on the way back it was -20F and the light came on. Same codes P0171 and P0174. Please keep us posted.

 

[Insane451]

I will let you know if the light comes back on or not in the next day or two my wife has the truck now because I'm working on her Taurus (replacing a water pump when it's been 8 degrees out is not fun) but ill have the truck on Sunday to go to work and back, 60 miles round trip, and if the light is going to come back on I think it would be after that long of a trip.

 

[Insane451]

Still no check engine light I don't want to jynx it but I think it was that air charge temp sensor that fixed it

 

[ukrboy]

Still no check engine light I don't want to jynx it but I think it was that air charge temp sensor that fixed it

Great to hear that. How hard was it to replace it?