In process of replacing all four 02 sensors & took off inner right fender. What appears to be some sort of vaccum lines are disconnected behind inner fender. Orange/Green/Black in triangular plug. Traced upwards - orange and green connect into firewall devices behind battery, black one is not connected at all. Any advice appreciated as to what they are. I had a new ECM put in 4-5 yrs ago, every so often Service ENgine light comes on; Corde P0172 & 175. code is cleared and stays off for months. 110K miles - King Rach Supercrew. Runs fine. Need to pass emissions & can't do so with check light on

Just want to learn what these lines may be before re-connecting & seeing what happens. Long term member here.... 19 yrs... glad to see site has grown & still active!

 

They are either for the climate control system or the 4wd system.

 

Thanks... turned out to be vacuum lines for 4 wd - orange & green connect to solenoids mounted on firewall behind battery, black tube apparently is a vent tube.