P0171 DTCS code...troubleshooting help?
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P0171 DTCS code...troubleshooting help?
My CEL came opn, and the code for P0171 popped up, System too lean Bank 1. I know that my #1 Cylinder is running too lean, and I'd like to know what the most common causes for this code popping up are. I've heard it is quite possibly an O2 sensor, But I don't want to play parts swap-out-circus until I get the facts straight. Basically, whats the list of easiest/cheapest parts to look at first? If in fact it is an O2 sensor, which one would I swap out? Thanks for the help ahead of time!!
Logistics Pro
Joined: Jan 2001
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From: Central NYS
The one that's causing the problem.
Of couse, I'm just josssing you. Let's start with the make, model, year, and engine.
Postmaster
Joined: Oct 2005
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From: NJ
Check for vacuum leak. I believe pcv is on pass. side (Bank 1). Check the rubber hoses going from pcv to intake. Oxygen sensor is a last resort IMO. Vacuum leak is one of the most common problems causing P0171 and P0174. Cleaning MAF is also a good suggestion. Sometimes that throws both P0171 and P0174 though.
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Elder User
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Maybe I don't know Fords well enough, but I thought Bank 1 was drivers side. I guess I work on too many GMs. If you already knew cy#1 was lean why didn't you solve that problem first? P0171 means Bank1 is lean. The O2 sensor doesn't know which or how many cylinders caused Bahnk 1 to go over the FTP standard, but the combined effect was enough to trigger the threshold value. You have to figure out if it's just cy#1 as you say or if there are other violators on Bank 1. Bank 2 is doing OK at this point so don't look for things in common to both banks like the MAP, IAT or MAF. What would cause cy#1 on Bank 1 to go lean and no others came along for the ride? Lean: Not enough fuel in ratio to the amount of air OR too much air in ratio to the amount of fuel. You're lean either way. Could you have a malfunctioning #1 injector(not enough fuel)? Could you have a vacuum leak(too much air)?
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Freshman User
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Sorry about the misconception. I assumed bank1 was #1 Cylinder. I am new to working on these types of engines, and I just bought a Chilton's to start troubleshooting (I have no idea where anything is on this truck). I am going to check the vacuum hoses and PCV valve for now. What would I use to clean the MAF? Never had to do anything like this on my car (Stealth). Will check back soon. Thanks for the advice so far!
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PCV Valve and all hoses checked out good, no leaks that I can find. One thing I noted was there is a buzzing noise when the truck is turned off for about 25 seconds right in the middle of the engine somewhere. Any idea about this?
Elder User
Joined: Aug 2004
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Bank one is the passenger side. Typically the front O2 sensor on that side is the first to let you know you have a problem so cleaning the MAF..etc and resetting the PMC would be a good start. How is the idle?
Postmaster
Joined: Oct 2005
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From: NJ
Should clear the code. You can disconnect battery for a minute or reset with a code scanner.
Also most recently working on a 98 F150 it had a P0171 code and turned out to be a bad injector o-ring. Try spraying carb. cleaner on injectors on pass. side and see if idle changes. Don't know if this is your problem but worth a shot to try.
Also most recently working on a 98 F150 it had a P0171 code and turned out to be a bad injector o-ring. Try spraying carb. cleaner on injectors on pass. side and see if idle changes. Don't know if this is your problem but worth a shot to try.