Abstract: A method for diagnosing an exhaust gas catalytic convertor and/or an exhaust gas sensor arranged downstream and/or upstream of the exhaust gas catalytic convertor in an exhaust gas system of a motor vehicle internal combustion engine. The internal combustion engine is operated with an air/fuel mixture having a substoichiometric air/fuel ratio. The internal combustion engine is switched off and an unfired towed operation with disabled fuel supply is performed in which air drawn in by the internal combustion engine is conveyed through the exhaust gas system to the exhaust gas catalytic convertor and exhaust gas sensor. The internal combustion engine is then operated with a substoichiometric air/fuel ratio and a signal of the exhaust gas sensor is evaluated with regard to a predefinable evaluation criterion, the signal being provided at least in a period of time between switch-off and the subsequent self-running of the internal combustion engine.