p0171 and p0174

[steelblueSE]

I keep getting these codes. I just installed a new maf about a month ago. The car drives fine, doesnt run rough or have any trouble starting. I kinda think a fuel filter is next on the list. Any ideas?

car is a 99 SE v6 w/158k

 

[MrHalaska2000CSVT]

Both of those code you gave are for the engine running too lean on bank 1&2 check for a vacuum leak that could affect the air after your MAF, like the vacuum lines ontoop of the UIM such as the brake booster line, and/or check for any vacuum leaks around the UIM and LIM, a quick way to check for this is to either use a propane torch (obviously not lite) or starter fluid and direct them around the UIM and LIM gaskets while having someone monitor the RPMs, if its just you take a camera and record the dash while you test it, and this should tell you if you have a vacuum leak causing your codes.

 

[NCSUmoomba]

Aren't these the codes that pop up when the pre-cats are "out of range"?

 

[BrApple]

Aren't these the codes that pop up when the pre-cats are "out of range"?

No. The codes for the pre-cats are P0420 and P0430. These codes indicate that they are not working in the "efficient range". These codes are for the upstream O2 sensors which control the A/F ratio.

These codes, together, generally indicate a vacuum leak or an issue with the MAF. If it was just one code then it could indicate that new O2 sensors are needed. The sensors still might need to be replaced. Some data logging of the sensors would help to understand that.

 

[steelblueSE]

I ended up swapping in a new MAF because it was still under warranty and then codes went away. It got traded in on Monday so it's someone else's problem now

 

[99_contour_svtt]

I have the P0174 System Too Lean (bank 2). I have used fuel injector cleaner to see if I could find the issue. I didn't hear my engine idle change.

 

[BrApple]

I have the P0174 System Too Lean (bank 2). I have used fuel injector cleaner to see if I could find the issue. I didn't hear my engine idle change.

fuel injector cleaner isn't going to make a difference. Chances are its time for a new O2 sensor. Try swapping the up stream sensors and see if you get a P0174. This would indicate that the sensor needs to be replaced.

 

[99_contour_svtt]

All the codes that I had before P0154, P0340, P0401, P0171 P0174 All the other codes have been corrected except the P0174 code. I had taken to a shop before after paying them then driving 60 miles home. I bought a new upstream sensor 2 weeks ago. If you spray throttle body cleaner into the throttle body it changes the idle. I didn't mean to put fuel injector cleaner. I used throttle body cleaner.

 

[projectSHO89]

"Lean" codes are not caused by O2 sensors, the sensors report the condition that is interpreted as 'lean".

Lean codes are usually caused by excessive un-metered air, from insufficient fuel supply, or incorrect data from the MAF sensor. With a V6, most likely the hoses around the IAC are the problem, but that depends on the year which was not reported.