What are the causes of high oxygen sensor voltage?

[CharlieFitz]

Oxygen sensor voltage is high due to: 1. Continuous low voltage signal may indicate issues such as overly lean air-fuel mixture or oxygen sensor malfunction; 2. Clogged fuel injectors where blocked injector nozzles can cause insufficient fuel injection in certain cylinders, leading to a lean mixture condition, and in severe cases, complete fuel injection failure; 3. Fuel pressure being too low - with a constant fuel pulse width, low fuel pressure reduces cyclic fuel injection quantity, resulting in a lean mixture; 4. Unmetered air between the mass air flow sensor and throttle body; 5. Intake manifold gasket leaks between the manifold and cylinder head, allowing undetected air by the manifold absolute pressure sensor, causing relatively reduced fuel injection and lean mixture; 6. Constant opening of the carbon canister purge solenoid valve in the evaporative emission control system.