P0170 OBD-II Code. What Does It Mean?

[KurleeDaddeeWRX]

I pulled a code for a fellow Bay Area I-club Member today, and his car came up with a P0170 code.

P0170 - Fuel Trim Bank 1

I found a little information on it but not enough to answer the question of what it is. I know we have a few SAE certified mechanics out there that might have access to books or databases that might be able to help out. What does the P0170 code mean exactly?

All help will be appreciated.

[KurleeDaddeeWRX]

To be more specific, the car in question is a 99' Impreza RS 2.5. It is running a Apexi S-AFC. The car has 82K miles on it.

Here is the information we have found on this code:

http://www.obdii.com/ubb/Forum1/HTML/000289.html

http://autos.groups.yahoo.com/group/...20782?source=1

http://forums.nasioc.com/forums/show...ighlight=P0170

http://forums.nasioc.com/forums/show...ighlight=P0170

http://forums.nasioc.com/forums/show...ighlight=P0170

I have suggested to him that he take out the S-AFC immediately and go back to the stock ECU with no mods. If the CEL comes up, then it has to be something else. I also asked him to check all the hoses and the intake circuit, as well as the vaccuum hoses for leaks.

Anything else?