P0171 code on 2004 Honda Accord (4 cylinder, automatic)
What is your question?
Hello, My 2004 Honda Accord has recently been giving my a P0171 CEL code on and off for the last few weeks, "Fuel System Too Lean (Bank 1)". Checking the short term fuel trim it gave me over 30% when idling, but under load it would go down to about 6%. I replaced the PCV valve and it has now gone down to about 22% while idling, and goes down to the same (6%) under load. I have Also replaced the main air intake boot, checked and cleaned the MAF, and vaguely checked for vacuum leak with no success. My air filter is still pretty new as well. I took my car to the dealer about 8 months ago to have a CEL diagnosed and they replaced a couple O2 sensors. I don't know what the code was but I'm guessing it was probably the same. I might notice a little loss in power but I never really payed attention to this, however my MPG seems to have taken a more noticeable hit. I dont want to just randomly throw money at my car, but get an opinion on what it could be first. Thanks, Andre
What makes this problem better or worse?
Short term fuel trim gets better under load. CEL light turns on after idling for a while, and turns off after driving for a while.
How long has your 2004 Honda Accord had this problem?
RepairPal Certified shops can diagnose and repair your 2004 Honda Accord. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Hello,
I appreciate that you have taken steps to try and troubleshoot.
One cause of concern could be debris in the mass air flow (MAF) sensor. It is important to not clean with a rag or using compressed air -- instead use a vacuum to clean any bugs / dirt / etc.
Another cause could be differing BARO values between the MAF and the MAP sensor. Do not throw parts at it; test it using a proper diagnostic tool and verifying specifications.
Also, i'm assuming you do not have an aftermarket intake installed, correct?
