Abstract: A method and a device for monitoring the functions of a sensor, in particular of a sensor for detecting a measurable value in a motor vehicle. If specified operating states exist, a measurable value is detected and compared to a reference value. Faults are detected when a measured value, held by the sensor, deviates by more than a tolerance value from a reference value. A measured value which had been detected and stored at an earlier instant when a corresponding operating state existed is used as the reference value.

Abstract: A fuel-metering system having a redundant control arrangement includes a main controller 12, an auxiliary controller 17, a first microprocessor 10, a second microprocessor 11, a switch-over unit 14, an actuator 15 and a fuel-metering unit 16. The second microprocessor emits a switch-over signal to the switch-over unit in the start phase of the internal combustion engine. The switch-over unit then supplies the actuator 15 with the actuator signal from the auxiliary control loop. A determination is made as to whether the actuator has reached the pregiven desired value. If this is indeed the case, then an indication is provided that the auxiliary controller and the switch-over unit are operating properly. If this is not the case, then the assumption can be made that the auxiliary controller or the switch-over unit is defective. In this case, a fault indication is provided.

Abstract: To permit ready matching of a Diesel engine operating circuit to a glow plug system, an interface-and-control unit (1) is provided which includes a microprocessor (MP) which decodes data words received from an engine control unit (MS). The data words are in the form of serially transmitted bits which define, by time duration of the bits. respectively logic "0" and logic "1" values to provide, inherently, simultaneously data information and synchronizing information. For example, the logic "0" bits may be 1/8 of a predetermined clock period (T) whereas the logic "1" bits may be 1/2 of the clock period (T). The microprocessor, thus, can be easily matched to engines of different types and can carry out, on its own, diagnostic routines and indicator functions under command of respective bits being transmitted thereto. Preferably, glow plug current is provided in pulsed form, the duty cycle of which is controlled by four data bits (D0-D4) transmitted to the microprocessor (MP).