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Bank 1 lean

  #1  
Old 01-01-2019, 10:55 AM
ashleyroachclip
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Bank 1 lean

Happy new year to all and good morning .
I have had my V10 scsb 4x4 for about 6 years now , a d finally something has gone wrong .
I say this , because after I have logged over 150k miles , and it having been flawlessly reliable , I am now getting a random bank 1 lean ses light .
By random , I mean I can drive several hundred miles , varying degrees of loads , and not have a check engine e light , then out of no where , light on .
I have read around for a common cause , and pcv hose or valve are a common reply.
I replaced the pcv hose and valve 6 months or so ago , checked it and it is firmly together and in place .
when I watch the live data on my scanner, my fuel trims are quite huge in comparison to what I have seen in the past when the truck was running perfectly .
by huge , I mean stft bank 1 is up in the 30's both positive and negative , while bank 2 is near 15 or less .
I dont remember ltft at the moment , but I seem to remember they were closer to normal in the 1.5 or so positive and negative swing .
This is a 99 with a manual 5 speed .
I dont just throw parts at any problem , hoping to fix the problem .
So now I just need to figure out , where the cause of the bank 1 vacuum leak is coming from ..
Any suggestions would be helpful .
Thanks .
 
  #2  
Old 01-01-2019, 11:18 AM
projectSHO89
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Short term fuel trims are supposed to be "all over the place" since they're reacting in near real time to varying conditions. You need to first look at your long term trims to see if they're relatively normal or biased well off from zero and whether or not they are close to each other or there's a wide difference. It is not uncommon for one bank to trip before the other with only a small differential between the trims.

So, check your freeze frame data to get a more complete picture of the conditions when the fault was detected. Posting that data would be useful for continued diagnostics.
 
  #3  
Old 01-01-2019, 07:46 PM
R&T Babich
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Originally Posted by ashleyroachclip View Post
.... I am now getting a random bank 1 lean ses light .
By random , I mean I can drive several hundred miles , varying degrees of loads , and not have a check engine e light , then out of no where , light on . ....
I had an intermittent bank 2 lean code awhile ago that turned out to be a loose exhaust pipe to manifold connection.

 
  #4  
Old 01-02-2019, 12:13 PM
ashleyroachclip
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I am trying to figure out how to get a freeze frame on my scanner .
I'll keep at that .
When truck als running properly , my trims were pretty close to even both banks .
Right now , the bank 1 is at idle , coolant temp at 187 f.
short term fuel -3.9 up to 0.6 ish
bank 2
-3.0 to 3.0
long term bank 1
3.9
bank
2 6.3
 


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