Trouble Code 171 & 174 - causing me trouble!
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New User
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Trouble Code 171 & 174 - causing me trouble!
I'm having fits with the check engine light. My 2000 Ranger is showing DTC's 171 and 174 which indicate that the engine is running lean. I subscribe to Alldatadiy online diagnostic service and have run their suggested tests to no conclusion.
I checked all hoses, fittings and gaskets for leaks - found none
Tested fuel pressure - it's Ok
Mass air flow sensor - appears OK
Here is the strange thing that I am finding. I have an engine scanner and it indicates that the barametric pressure sensor is reading much lower than it should (22 in. Hg as oppose to 30 in. Hg). They have a specific test to do on this sensor but I'll be dammed if I can find it. Alldatadiy gives not-a-clue to where to find it.
Does this truck have a separate barometric pressure sensor or is it part of some other part or sensor? Any help with this would be greatly appreciated.
Any thought on what to check to fix these code would also be appreciated. I think i have checked most of the obvious stuff but I'm missing something.
I checked all hoses, fittings and gaskets for leaks - found none
Tested fuel pressure - it's Ok
Mass air flow sensor - appears OK
Here is the strange thing that I am finding. I have an engine scanner and it indicates that the barametric pressure sensor is reading much lower than it should (22 in. Hg as oppose to 30 in. Hg). They have a specific test to do on this sensor but I'll be dammed if I can find it. Alldatadiy gives not-a-clue to where to find it.
Does this truck have a separate barometric pressure sensor or is it part of some other part or sensor? Any help with this would be greatly appreciated.
Any thought on what to check to fix these code would also be appreciated. I think i have checked most of the obvious stuff but I'm missing something.
Post Fiend
Joined: Oct 2005
Posts: 5,242
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From: Kiev, Ukraine
well, I had. '01 4.0 SOHC. had many problems together, dirty MAF+dirty fuel sender + cloged cat + vac. leak +bad EGR + bad spark plugs and wires. How did I understand that plugs are bad? Emission test read lean mixture and very hight CxHx concentration. All problems together and lamda control limit is got. ANd I got lean codes with missfire codes.
I changed all bad parts and cut out cat.converter. RUns really fine
I changed all bad parts and cut out cat.converter. RUns really fine
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
There is no BARO sensor on Ford MAF-equipped vehicles, except for the Supercharged 3.8L and the Taurus SHO 3.0L.
Check out: https://www.ford-trucks.com/forums/s...52&postcount=1
See also: https://www.ford-trucks.com/forums/1...-cleaning.html
Check out: https://www.ford-trucks.com/forums/s...52&postcount=1
See also: https://www.ford-trucks.com/forums/1...-cleaning.html
Cargo Master
Joined: May 2004
Posts: 3,007
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P0171- System to Lean (Bank 1)
P0174- System to Lean (Bank 2)
The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.
Possible Causes are Fuel system, Excessive fuel pressure, Leaking/contaminated fuel injectores, Leaking fuel pressure regulator, Low fuel pressure or running out of fuel, Vapor recovery system, Induction system, EGR system, Base Engine.
Check intake air system for leaks, obstructions and damage
Check air cleaner element, air cleaner housing for blockage
Verify integrity of the PCVsystem
Check fuel delivery system and filter for restriction
Check for Vacuum leaks
Check Fuel Pressure
Check Fuel Injectors
P0174- System to Lean (Bank 2)
The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.
Possible Causes are Fuel system, Excessive fuel pressure, Leaking/contaminated fuel injectores, Leaking fuel pressure regulator, Low fuel pressure or running out of fuel, Vapor recovery system, Induction system, EGR system, Base Engine.
Check intake air system for leaks, obstructions and damage
Check air cleaner element, air cleaner housing for blockage
Verify integrity of the PCVsystem
Check fuel delivery system and filter for restriction
Check for Vacuum leaks
Check Fuel Pressure
Check Fuel Injectors
Postmaster
Joined: Oct 2009
Posts: 3,432
Likes: 7
Here is the strange thing that I am finding. I have an engine scanner and it indicates that the barametric pressure sensor is reading much lower than it should (22 in. Hg as oppose to 30 in. Hg). They have a specific test to do on this sensor but I'll be dammed if I can find it. Alldatadiy gives not-a-clue to where to find it.
Any thought on what to check to fix these code would also be appreciated. I think i have checked most of the obvious stuff but I'm missing something.
Excessive fuel pressure will not result in lean codes, but low pressure can. A plugged fuel filter comes to mind, but a weak pump or faulty regulator belong on the list too.
When you say you checked for leaks, you did not indicate how. Spraying starter fluid or propane around the intake will not always find a leak. So that method is not 100% conclusive just because you didn't get a result. A smoke machine should be able to find even the smallest leaks.
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Thanks for the replies. I live at 1000 ft. above sea level so a BARO reading of 22 seem very low. The MAF sensor is new so if the BARO sensor is part of it than it's new also.
I check for leaks visually (checked air tube, vacuum line, PCV system). I sprayed brake cleaner on all the gasket surfaced that I could reach and got no change in engine rpms. Additionally, TSB 04-17-04 runs through a process to see if a leak is causing the problem. The test procedure compares the short and long term fuel trim at idle and then at 2500 rpm. If the values don't change much (less than 15%), a leak is not suspected.
The darnest thing is that the truck runs great and has since I bought it new. The one possibility mentioned below that I have not checked is Leaking/contaminated fuel injectores. That will be my next adventure.
I check for leaks visually (checked air tube, vacuum line, PCV system). I sprayed brake cleaner on all the gasket surfaced that I could reach and got no change in engine rpms. Additionally, TSB 04-17-04 runs through a process to see if a leak is causing the problem. The test procedure compares the short and long term fuel trim at idle and then at 2500 rpm. If the values don't change much (less than 15%), a leak is not suspected.
The darnest thing is that the truck runs great and has since I bought it new. The one possibility mentioned below that I have not checked is Leaking/contaminated fuel injectores. That will be my next adventure.
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