Any other reasons for P0171, P0174 Codes?
#1
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Hello,
Still working to clear the DTC codes on my 2003 XJR. I'm now down to these two codes: P0171 & P0174; "System too lean bank 1" "System too lean bank 2". Besides vacuum leaks,, is there any other reason for the car to throw these codes? The fuel trims are tolerable in idle but the short trim especially goes high on acceleration. I had tried a smoke test though probably the smoker did not have enough volume to really press a large quantity into the throttle body but still, did not see any smoke coming from anywhere. The O2 sensors seem to be showing some numbers when the accelerator is pressed so I'm not convinced there's anything wrong there. Besides, I'd get a code if any were failing.
Not sure what else to check at this point.
Lastly, I hear a very faint high frequency squeal coming from the brake booster while the car is running. I removed the vacuum line and taped it shut to test to see if the trims would settle down. There was no noticeable FT change at all with the vacuum line closed.
Has anyone ever had an issue with the booster failing? Even though the trims did not change, is there any reason to suspect the booster is causing the problem?
Thanks much, Dave
Still working to clear the DTC codes on my 2003 XJR. I'm now down to these two codes: P0171 & P0174; "System too lean bank 1" "System too lean bank 2". Besides vacuum leaks,, is there any other reason for the car to throw these codes? The fuel trims are tolerable in idle but the short trim especially goes high on acceleration. I had tried a smoke test though probably the smoker did not have enough volume to really press a large quantity into the throttle body but still, did not see any smoke coming from anywhere. The O2 sensors seem to be showing some numbers when the accelerator is pressed so I'm not convinced there's anything wrong there. Besides, I'd get a code if any were failing.
Not sure what else to check at this point.
Lastly, I hear a very faint high frequency squeal coming from the brake booster while the car is running. I removed the vacuum line and taped it shut to test to see if the trims would settle down. There was no noticeable FT change at all with the vacuum line closed.
Has anyone ever had an issue with the booster failing? Even though the trims did not change, is there any reason to suspect the booster is causing the problem?
Thanks much, Dave
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#5
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In another source I found a recommendation to change the fuel cap on my 2013 Jaguar XF AWD 3.0L (X250) with a genuine Jaguar fuel cap, no generic after market units. I thought, what the heck, I've tried everything else. Immediately after I installed the new fuel cap, and deleted the previous codes, the problem went away. Interesting at best. I would gather this is due to the pressurization of the fuel tank. Just an idea.
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#8
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Well, you are the SFT trim winner! I had replaced the fuel pressure regulator last fall with an adjustable after market unit. When you mentioned the regulator, I increased the pressure to 41Lbs and that settled the SFT numbers into normal range! Now all the DTCs have been resolved on my XJR! Wow!
Really great advice from this group! Can't thank you all enough....
Really great advice from this group! Can't thank you all enough....
#10
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amchestnutesq
XJ XJ6 / XJ8 / XJR ( X350 & X358 )
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04-06-2023 11:13 AM
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