2005 throwing lean code
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2005 throwing lean code
hey guys i got my 1st superduty few months ago. its been a great truck. the other day it threw a p0174 lean code. i searched but couldn't find anything 5.4 specific? where do i start to fix this? its a 2005 5.4l thanks in advance
Senior User
Joined: Oct 2011
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From: kentucky
try changing the fuel filter if u havent lately my sons 5.4 threw a lean code filter fixed it
Laughing Gas
Joined: May 2008
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From: Central Kansas
I had that code as well as a miss and it was an injector. They had a problem w/ injectors in 2005 w/ the 5.4. They are covered under an extended warranty though if it does turn out to be an injector so it shouldn't cost you anything. Try the fuel filter first though, they're super easy to change on the 2005, don't need the special tools anymore.
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i just changed the fuel filter about a month ago. . the truck has 137000 on it. will the injector warrenty still cover it if its a injector? i do not know when the last time the plugs or coils have been done. could it be the plugs? or possibly a o2 sensor gone bad? how do you test for fuel pressure on this? i dont see a test port on the fuel rail. thanks
Laughing Gas
Joined: May 2008
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From: Central Kansas
Sorry, nevermind. The extended injector warranty is 11 years or 120,000miles. There's not a test port to check fuel pressure w/ a gauge like on the older 2 vales, it's all read w/ sensors so you'll need a scanner of some sort. I think the Scangauge can do it.
Could be plugs, when's the last time they were changed? Hopefully they're not the originals or you could have a time getting them out w/out breaking them. Could probably be an 02 sensor too, I think they can be tested but I'm not sure how. I know that will also take a scanner of some sort. Hopefully someone more knowledgable chimes in soon to help you...
Could be plugs, when's the last time they were changed? Hopefully they're not the originals or you could have a time getting them out w/out breaking them. Could probably be an 02 sensor too, I think they can be tested but I'm not sure how. I know that will also take a scanner of some sort. Hopefully someone more knowledgable chimes in soon to help you...
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update found scanner
ok i found a scanner the fuel pressure is at 40 psi. is that right? the o2 sensors are reading the same voltage between bank 1 and bank 2. someone told me it could be a pcv valve? i have a bunch of freeze frame data but i dont know what it means. how do you read fuel trims? long vs short term? those seem out of wack between bank 1 and 2 but i dont know what is correct? thanks for any help.
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Laughing Gas
Joined: May 2008
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From: Central Kansas
Here's the specs for the trims from the 2005 service manual, sorry about the formatting, but it looks like it doesn't matter.
Sensors/Inputs PCM Pin/PID only Units Measured/PID
KOEO Hot Idle 48 KM/H (30 MPH) 89 KM/H (55 MPH)
LONGFT1 PID (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 %
LONGFT2 PID (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 %
SHRTFT1 PID (L) (-)10-(+)10 (-)10-(+)10 (-)10-(+)10 %
SHRTFT2 PID (L) (-)10-(+)10 (-)10-(+)10 (-)10-(+)10 %
Typical Fuel Monitor Malfunction Thresholds:
Lean Malfunction: LONGFT greater than 25%, SHRTFT greater than 5%.
Rich Malfunction: LONGFT less than 25%, SHRTFT less than 10%
Fuel pressure spec is listed as 35-70psi (240-485kpa)
Sensors/Inputs PCM Pin/PID only Units Measured/PID
KOEO Hot Idle 48 KM/H (30 MPH) 89 KM/H (55 MPH)
LONGFT1 PID (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 %
LONGFT2 PID (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 (-)20-(+)20 %
SHRTFT1 PID (L) (-)10-(+)10 (-)10-(+)10 (-)10-(+)10 %
SHRTFT2 PID (L) (-)10-(+)10 (-)10-(+)10 (-)10-(+)10 %
Typical Fuel Monitor Malfunction Thresholds:
Lean Malfunction: LONGFT greater than 25%, SHRTFT greater than 5%.
Rich Malfunction: LONGFT less than 25%, SHRTFT less than 10%
Fuel pressure spec is listed as 35-70psi (240-485kpa)
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figured it out!!!!!
i finally figured out the lean code. it ended up being a lazy o2 sensor after the cat. i checked for vacuum leaks but couldn't find any. finally got a good scanner and could look at o2 live data and found a lazy o2 sensor. thanks for the help
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the code is back.
the code is back. 
. the code stayed off for 200 miles and is now back. what else can i check? why would changing the o2 sensor turn it off for 200 miles if it wasnt causing the problem? just shear luck? you could see on the scanner that the o2 was reading slow.. im running outa ideas? should i just take it to the dealer? will their scanner tell exactly whats wrong? i just want it fixed
. the code stayed off for 200 miles and is now back. what else can i check? why would changing the o2 sensor turn it off for 200 miles if it wasnt causing the problem? just shear luck? you could see on the scanner that the o2 was reading slow.. im running outa ideas? should i just take it to the dealer? will their scanner tell exactly whats wrong? i just want it fixed
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Joined: Jun 2008
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From: Wayyy NoCal, USA
Unfortunately, lean is a symptom, not a root cause - and I don't think their scanner will give any more details. However, an experienced and knowledgable expert will know which are the most likely suspects and narrow down the list of suspects to minimize trial and error solutions.
As with any car or truck, the challenge is finding an experienced and knowledgable expert! Many "mechanics" are not. And paying more at a dealership does not mean they are any better. Some dealers hire the best, some higher the cheapest. Same with independent shops. Ask around and find out who is good in your area. And remember that if they are really good, they are not really cheap.
As with any car or truck, the challenge is finding an experienced and knowledgable expert! Many "mechanics" are not. And paying more at a dealership does not mean they are any better. Some dealers hire the best, some higher the cheapest. Same with independent shops. Ask around and find out who is good in your area. And remember that if they are really good, they are not really cheap.
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