Been getting both &either current or pending for some time, cleaned MAF then replaced it. Used a bottle of Techtron.


Monitoring MAF flow, short and long term fuel trim and leading O2 sensor for both banks. Not seeing anything unusual.


DTC says set by out of range fuel trim but not seeing that, short and long term values are close and getting over 20mpg. Plenty of power.


Any suggestions ? Would expect manifold leak to show up as O2 value and fuel trim request but nada. Ran about 150 miles yesterday and didn't appear until in stop and go traffic Idles smoothly at 600 rpm light on or off.

 

Incidentally it starts/runs very well, smooth 600 rpm idle in gear, good power to redline, 24mpg on last tank.


Just codes keep coming back.

 

Dumb question , but... Is air filter seated good , good gasket an seated in both places? At low idle with the light coming on its something,small , maybe dirty sensor. Your doing Techron , maybe cataclean?

 

Both air filters are new and properly seated. Cleaned first MAF sensor several times but codes kept coming back so replaced with new Bosch MAF. Codes now take a day or two to appear but keep coming back.


Short Term Fuel trim is normally in the +2.0 to +3.0 range but have seen jump momentarily -8.0 to -10.0 for less than a second (both banks). Have not seen an accompanying change in either O2 sensors or MAF flow reading. Coolant temps is stable and correct. Not sure what else to monitor but something is making the trims jump occasionally.

 

ps fuel pressure when running is a bit over 50psi and stable MAP is varying with load.

 

Have you changed the injectors? I went to 550's and I have the same issue, codes only after idling awhile. I have an Ultra gauge so resetting is easy. I believe that the issue is the bigger injectors can't deliver a small enough charge so it's just a bit rich at idle.

 

No, everything is stock. Seems to be slowing down. After driving all day were just "pending" and not set.

 

It is the computer learning, the codes will come longer and longer between then eventually they will stop.