This truck doesn't get driven much anymore. Less than 1k last year. Got in it the other day and the check engine light came on. Took it to Auto Zone to have codes read. Came up with: P0442, Evaporative emission system- Small leak/ no flow condition. Probable cause: Defective or loose fuel cap. took it off, checked it, looks good, put it back on tight, engine light still on. Don't have a clue where to begin with the following: Evap canister or hose cracked-not connected. Purge or vent solenoid defective. Vacuum leak at engine. P3400, Cylinder deactivation system performance. The control module detects that the actual measured values from the MAF sensor, MAP sensor, and TP sensor, is not within the range of the calculated values for V4 mode. What??? The truck seems to be running fine, and goes in and out of V4 mode when cruising as it always has done. Has anyone had experience with these codes? What did you do to fix it? I was a good mechanic back in the points, plugs and condensers days. Totally clueless now.