Abstract: A method for monitoring a coolant temperature sensor of a motor vehicle is provided, wherein an actual value (TCOist=TCOSt) of a coolant temperature (TCO) is determined by a coolant temperature sensor when an internal combustion engine of the motor vehicle is started (t=tSt), and the coolant temperature sensor is diagnosed as a functional coolant temperature sensor if the actual value (TCOist) of the coolant temperature (TCO) drops briefly (tmin0) when the internal combustion engine is started (t=tSt). A controller, e.g., an engine controller, for performing such method is also provided.

Abstract: A method for monitoring a coolant temperature sensor of a motor vehicle is provided, wherein an actual value (TCOist=TCOSt) of a coolant temperature (TCO) is determined by a coolant temperature sensor when an internal combustion engine of the motor vehicle is started (t=tSt), and the coolant temperature sensor is diagnosed as a functional coolant temperature sensor if the actual value (TCOist) of the coolant temperature (TCO) drops briefly (tmin0) when the internal combustion engine is started (t=tSt). A controller, e.g., an engine controller, for performing such method is also provided.

Abstract: An internal combustion engine has an exhaust gas tract with a first and a second exhaust gas catalyst downstream of the first one, a first exhaust gas sensor, which is disposed upstream or in the first catalyst, and a second exhaust gas sensor, which is disposed downstream of the first catalyst and upstream of the second catalyst. During trailing throttle operation, the measurement signal of the second sensor is monitored for a signal characteristic that is typical of a maximum possible saturation state with oxygen that the first catalyst can achieve, upon which a characteristic variable is determined for a saturation state of the second catalyst with oxygen as a function of an engine operating variable. Outside the trailing throttle operation, an enrichment mode is controlled by enriching the air/fuel mixture, specifically as a function of the characteristic variable for the saturation state of the second catalyst with oxygen.

Abstract: In a method for monitoring a coolant temperature sensor and/or a cylinder head temperature sensor of a motor vehicle, during a start (t=tSt) of an internal combustion engine of the motor vehicle an actual value (TCOist=TCOSt) of a coolant temperature (TCO) is determined by a coolant temperature sensor, and an actual value (TCYLHist=TCYLHSt) of the cylinder head temperature (TCYLH) is determined by a cylinder head temperature sensor, wherein the coolant temperature sensor and/or the cylinder head temperature sensor are diagnosed as functional sensors when the actual values (TCOist, TCYLHist) of the coolant temperature (TCO) and the cylinder heat temperature (TCYLH) deviate in the same direction upward in relation to an outside temperature (TAM) and/or an intake air temperature (TIA). By a control device, particularly a motor control device, a method can be and is carried out accordingly.

Abstract: In order to diagnose a coolant pump (11) which is provided for the purpose of circulating a coolant in a closed cooling circuit of an internal combustion engine (10) and which can be activated and deactivated independently of the operating state of the internal combustion engine (10), both a value representing the coolant temperature (TCO) of the internal combustion engine (10) and a value representing the cylinder head temperature (TZK) of the internal combustion engine (10) are determined at a predefined time instant (t2) after a cold start of the internal combustion engine (10) has been detected and the values are subsequently compared with each other. The coolant pump (11) is rated in terms of its operational integrity as a function of the result of the comparison. This enables a faulty coolant pump to be detected at a very early stage after a cold start of the internal combustion engine.

Abstract: In order to diagnose a coolant pump (11) which is provided for the purpose of circulating a coolant in a closed cooling circuit of an internal combustion engine (10) and which can be activated and deactivated independently of the operating state of the internal combustion engine (10), both a value representing the coolant temperature (TCO) of the internal combustion engine (10) and a value representing the cylinder head temperature (TZK) of the internal combustion engine (10) are determined at a predefined time instant (t2) after a cold start of the internal combustion engine (10) has been detected and the values are subsequently compared with each other. The coolant pump (11) is rated in terms of its operational integrity as a function of the result of the comparison. This enables a faulty coolant pump to be detected at a very early stage after a cold start of the internal combustion engine.

Abstract: An internal combustion engine has an exhaust gas tract with a first and a second exhaust gas catalyst downstream of the first one, a first exhaust gas sensor, which is disposed upstream or in the first catalyst, and a second exhaust gas sensor, which is disposed downstream of the first catalyst and upstream of the second catalyst. During trailing throttle operation, the measurement signal of the second sensor is monitored for a signal characteristic that is typical of a maximum possible saturation state with oxygen that the first catalyst can achieve, upon which a characteristic variable is determined for a saturation state of the second catalyst with oxygen as a function of an engine operating variable. Outside the trailing throttle operation, an enrichment mode is controlled by enriching the air/fuel mixture, specifically as a function of the characteristic variable for the saturation state of the second catalyst with oxygen.