PO171 & PO174 codes on QX4

[John S]

Hello,Just wanted to pass on my problem and solution. Check engine light on with following codes PO171 & PO174 codes on QX4 when reading with my OBD computer reading program. Left sidedowstream o2 voltage read on average less than .10 replaced it and MIL light came back on with same codes. Bought some MAF sensor cleaner and sprayed the hell out of it, even used a Q-tip. Reset MIL and problem solved. Hope this might help someone else.

[Infinitiguy19]

http://www.obd-codes.com/p0171

http://www.obd-codes.com/p0174

[Chuck Tribolet]

Those codes are lean on left side, lean on right side. When you get a leanconditions on BOTH sides, it's likely something common to both sides, e.g.,not an O2 sensor. And it's definitely not the downstream O2 sensor whosejob is to make sure the cat is good. Upstream O2 sensor is the one that reportslean/rich.

Chuck

[tbsbiker2]

Ive been chasing this one too. I have new coil packs already so hoping this isnt the issue. at times I would have a bit of a rought idle on start but only Got Lean Bank 1 if I drove on the HWY for extended period of time over 60 MPH... so I first changed the fuel filter (My MAF and stock Air filters are clean), reset code and it went away until the next hwy trip...then I tried the Maxima MAF $105.00 figured couldn't hurt...my MPG went UP 2 MPG CAR RUNS GREAT but today got the code again...so Probably Sensor (wil l need to check with OBD scanner again)...what a PIA...I've drivin this thing for 2+ years without any codes and now I can't get them to dissappear.

Cant find any vacume leaks.

[Pathfinder01Babe]

01 Nissan Pathfinder with a little over 150,000 miles. SES light starting coming on and off about six months ago. At first around fueling or needing fuel. Tried fuel additive and higher octane...no difference..on and off again. Had to have my water pump replace so I had the system check for vacum leaks...none. Light started staying on all the time and emissions due next month, so I pulled the MAF sensor this weekend and cleaned (drenched) it with electrical cleaner (hit the wiring harness contact also). Replaced the air filter with a cotton filter as I have read that some high end filters contain some silicone that mucks up the MAF. Had Adavance Auto run the codes and reset the light for me and drove it on interstate this weekend....no light, no problem. Will probably go get a new gas cap too. You will need a Torx T20 with a security (hole in middle) bit to pull off sensor.