P0174B Code? Check this first.
After using your site to diagnose my girlfriend's truck I felt it only fair that I post the pleasantly simple solution that I found. At about 80,000 miles, coincidentally after replacing the original spark plugs, her Check Engine light came on. The truck was due for an oil change so when we took it in we asked the shop to read the code for us. They were nice enough to do this for free. The code came up as P0174B.
I searched several sites looking for possible causes of this code. It can be any number of things from failed intake gaskets to dirty sensors. As it turned out, however, it was something not mentioned on any of the sites I visited. It was a simple vacuum leak caused by a failed seam on a vacuum line elbow fitting. The part that failed is located toward the front of the intake partly under the throttle plate/valve. It is a 90 degree rubber hose with about a 5/8 inch inside diameter. We could have fixed it with duct tape but since she bought the truck new she wanted the correct parts. The part was about $50 and took only minutes to install. It is #KCV-190 4L5Z-6758-HA.
After installing the new line, the truck starts and runs perfectly. To turn off the check engine light, we disconnected the battery, stepped on the brake pedal and turned the key to the start position for about 30 seconds. This drained the capacitors holding the memory of the code. The light has not come back on.
I will try to post photos.
Thanks for a great site,
Brennan R. Cook