02F-1504x4

My moms 05 f-150 has one more issue. The 4x4 worked great when she first got it. They hardly use it except when needed. Now it will not go into 4H or 4L. She has gotten it in ounce for the past few weeks we have been trying but never again. We checked fuses and the obvious. Any secret problems I should know about?

Thanks.

rubber314chicken

The vacuum pump that performs the change might have a leak somewhere. If I'm not mistaken it is mounted on the firewall passengers side.