2001 GMC 1500 Pickup PO446 DTC: EVAP System Leak or Electrical Issue?
I recently purchased a 2001 GMC 1500 pickup and am seeing a diagnostic code PO446. My service manual indicates this code corresponds to an 'EVAP system computer output circuit' fault. I took the vehicle to a local recommended shop, who suggested it might be due to a leak in the evaporative emission control system. However, my owner's manual lists multiple specific EVAP leak codes—should I focus on identifying physical leaks (such as in the gas cap, charcoal canister, purge solenoid, vent solenoid, or vacuum lines), or is an electrical issue more likely given the PO4406 code description?
The most common cause of PO446 in a 2001 GMC 1500 is often a faulty level or pressure sensor located at the top of the fuel pump. I'll verify this with further diagnostics and update you accordingly.