I have a 2002 expedition 5.4L XLT and about a week and a half ago I got the p0171 and p0174 codes so I cleaned the MAF and throttle body I looked for vacuum leaks and couldn't find any and the check engine light was reset. We drove my truck over 1500 miles over thanksgiving and the whole time the light stayed off and now it's back. The only symptom I have is excessive fuel consumption, it used a quarter tank to go 60 miles yesterday. No rough idle, which is what I would expect if I had a vacuum leak based on past experience with vacuum leaks, it runs great and idles smooth. The only other condition was the first time the light came on we were in below freezing temps in Iowa and we drove to Oklahoma where it was in the 60's and 70's all week and then when the light came back on last night we were in below freezing temps again in Iowa. I'm going to clean the MAF again today and reset the codes. Any help would be great thank you.
P0171 p0174 codes please help
- Thread starter Insane451
- Start date
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Bedrck47
Full Access Members
The following was copied from the 2002 Ford Service Manual
P0171 - System to Lean (Bank 1)
The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.
Air Measurement System
MAF sensor (contaminated, damaged, malfunctioning, etc.)
Fuel System
Fuel pressure regulator (leaking, malfunctioning, etc.).
Fuel filter plugged, dirty.
Fuel pump (weak, check valve leaking, etc.).
Leaking/contaminated fuel injectors.
Low fuel pressure or running out of fuel.
EVAP canister purge valve leaking (when canister is "clean").
Fuel supply line restricted.
Fuel rail pressure sensor (incorrect reading).
Air Induction System
Air leaks after the MAF.
Vacuum Leaks.
PCV system (leak, valve stuck open, etc.)
Improperly seated engine oil dipstick.
Exhaust System
Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets, etc.)..
EGR System
EGR valve tube/gasket leak
EVR solenoid vacuum leak
Secondary Air Injection
Damaged/malfunctioning secondary air injection system (mechanically stuck valve).
View Freeze Frame Data to determine operating conditions when DTC was set. Observe LONGFT1 and 2 PID(s). Refer to Section 2 , Adaptive Fuel DTCs Diagnostic Techniques for more information.
P0174 - System to Lean (Bank 2)
The Adaptive Fuel Strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.
See Possible Causes for DTC P0171.
See Diagnostic Aides for DTC P0171
P0171 - System to Lean (Bank 1)
The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.
Air Measurement System
MAF sensor (contaminated, damaged, malfunctioning, etc.)
Fuel System
Fuel pressure regulator (leaking, malfunctioning, etc.).
Fuel filter plugged, dirty.
Fuel pump (weak, check valve leaking, etc.).
Leaking/contaminated fuel injectors.
Low fuel pressure or running out of fuel.
EVAP canister purge valve leaking (when canister is "clean").
Fuel supply line restricted.
Fuel rail pressure sensor (incorrect reading).
Air Induction System
Air leaks after the MAF.
Vacuum Leaks.
PCV system (leak, valve stuck open, etc.)
Improperly seated engine oil dipstick.
Exhaust System
Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets, etc.)..
EGR System
EGR valve tube/gasket leak
EVR solenoid vacuum leak
Secondary Air Injection
Damaged/malfunctioning secondary air injection system (mechanically stuck valve).
View Freeze Frame Data to determine operating conditions when DTC was set. Observe LONGFT1 and 2 PID(s). Refer to Section 2 , Adaptive Fuel DTCs Diagnostic Techniques for more information.
P0174 - System to Lean (Bank 2)
The Adaptive Fuel Strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.
See Possible Causes for DTC P0171.
See Diagnostic Aides for DTC P0171
I understand what the codes mean what I want to know is why it would be gone for over a week after cleaning the MAF and driving over 1500 miles, I know it doesn't take that long for the computer to reset. Is it possible my MAF is going bad? That is the only thing I did was clean the MAF and it seemed to be fine for that long trip and for a week and a half. I have no rough idle no surges no other symptoms that point to vacuum leak or not getting enough fuel.
GaWag
Member
I fought these same codes. Intermittent check engine light. Cleaned and replaced maf. No vacuum leaks. No cracks.
In the end, the solution was a 10 dollar fuel filter. Once I pulled it, more black crap came out than fuel. I had over 270,*** miles as well. Drive like a champ afterward. If you've never change it, it's an easy and cheap fix. Should be done anyway.
In the end, the solution was a 10 dollar fuel filter. Once I pulled it, more black crap came out than fuel. I had over 270,*** miles as well. Drive like a champ afterward. If you've never change it, it's an easy and cheap fix. Should be done anyway.
american steel
Full Access Members
look at your vacuum hoses and valves.
Yudaman
Full Access Members
Start with the fuel filter. A clogged filter could easily cause lean conditions.
Besides, who knows when it was changed last...
Besides, who knows when it was changed last...
Ok so far what I have done after the light came back the second time is clean the MAF again replaced fuel filter, the old one looked like it was still new. I've looked for vacuum leaks, couldn't find any. The light hasn't come back on yet but it did take over a week for it to come back on the first time. If the light comes back on I think I'll replace the MAF. Is there anything else I should look into or check? It's just a waiting game right now to see if the light comes back.
Ok it has been 2 weeks and one day since I posted and today the light came back on same codes. I cleaned the MAF and had the fuel filter changed in those 2 weeks. I know it doesn't take that long for the computer to reset. In those 2 weeks we had warmer weather in the 40s and 50s then the other day it dropped to below 30s again and now my light is back on. So I'm back to where I was before thinking it's either a MAF that's on its way out but still works off and on or its related to how cold it is. Every time the light comes on its below freezing and stays off when it's above freezing. Now that may just be a coincidence but it is what's happening. I'm still open to suggestions please help.
Bedrck47
Full Access Members
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
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Bedrck47
Full Access Members
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
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
Member
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.
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csdangerous
Member
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...
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
Full Access Members
Keep us posted to the results Thanks
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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.
Great to hear that. How hard was it to replace it?
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