The dreaded po171 code
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Junior Member
Joined: Oct 2013
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The dreaded po171 code
The other day I was driving home from work and SES light came on, so I went by the local auto parts store and had them scan it.. So it happens to be the dreaded po171 code everyone is having.... The truck idles real rough around 500rpms, and when approaching a stop light the lights dim and drops lower than 500 almost like its going to die.. When accelerating its real sluggish and shakes with no power.. There is a bad squeaking sound almost coming from under the hood while driving but not while in park.. So I started looking for a vacuum leak and no luck... I replaced the PCV hose and valve and changed the IAC valve, and don't want to keep through parts at it... The truck is a 2002 ford f150 from Arizona and has 150k on the clock.. I live in Indiana and the weather has been really nasty, don't know if that would cause anything..
But I appreciate all the help in advance..
But I appreciate all the help in advance..
Senior Member
Joined: Jan 2014
Posts: 414
Likes: 27
I got the same code last week. What I did was measure the LT FTRM1 and LT FTRM2 using the live data setting on my code reader. You have to make sure you wait to measure until the coolant temperature (also on live data) is warmed up enough. about 85 degrees +
From what I understand, the reading is supposed to read 5-10, (%) and then bottom out at a negative integer.
Mine read 24 and bottomed out at about 7. Which is clearly too high on both ends. This confirms there is a leak somewhere.
In my case, luckily, one of the hoses on my intake had come off from the backside where it is very hard to see and upon putting back in place the numbers went down to normal and my truck was great. Goodluck
From what I understand, the reading is supposed to read 5-10, (%) and then bottom out at a negative integer.
Mine read 24 and bottomed out at about 7. Which is clearly too high on both ends. This confirms there is a leak somewhere.
In my case, luckily, one of the hoses on my intake had come off from the backside where it is very hard to see and upon putting back in place the numbers went down to normal and my truck was great. Goodluck
Senior Member
Joined: Jun 2013
Posts: 272
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Im having similar issues with mine po171 and po174. Ive replaced 3 of the 4 o2 sensors and it ran great for a few days and threw the same codes this morning. I havent had a chance to check for a leak yet, but the print out i got from autozone said if both codes come together to check the MAF and fuel pressure. It does idle rough when its cold, but once its warm its better. Still a little rough at stop lights though. I have lost mpgs, but i still feel like it has power, but it has started to shift into OD going up hills now when it didnt use to. Should i spray for leaks as well? And if no leaks, woukd a MAF from my local JY be ok to try out? Not trying to hijack the thread since we're having the same issue. I have an 01 5.4 with 227k miles. Thanks guys!
Senior Member
Joined: Jan 2014
Posts: 414
Likes: 27
Im having similar issues with mine po171 and po174. Ive replaced 3 of the 4 o2 sensors and it ran great for a few days and threw the same codes this morning. I havent had a chance to check for a leak yet, but the print out i got from autozone said if both codes come together to check the MAF and fuel pressure. It does idle rough when its cold, but once its warm its better. Still a little rough at stop lights though. I have lost mpgs, but i still feel like it has power, but it has started to shift into OD going up hills now when it didnt use to. Should i spray for leaks as well? And if no leaks, woukd a MAF from my local JY be ok to try out? Not trying to hijack the thread since we're having the same issue. I have an 01 5.4 with 227k miles. Thanks guys!
Try live data first and make sure its a leak.
