A test method for an exhaust gas probe (8, 9) of an internal combustion engine (3), particularly for a lambda probe, has the following steps: Checking an output signal (λ1, λ2) of the exhaust gas probe (8, 9), detecting a fault state of the exhaust gas probe (8, 9) on the basis of the output signal (λ1, λ2) of the exhaust gas probe (8, 9) and differentiating between different fault states of the exhaust gas probe (8, 9).