Various methods and systems are provided for diagnosing an engine component based on a measured engine speed during an engine shutdown event. As one embodiment, a method for an engine includes measuring an engine speed drop rate, via an engine speed sensor, during an engine shutdown event; and indicating a change in performance of one of the engine speed sensor or an additional engine component in response to the measured engine speed drop rate deviating from a reference engine speed drop rate by a pre-set or pre-defined threshold rate.

A lawn care device may include an engine to selectively power the lawn care device, a frame supporting the engine of the lawn care device, an ignition system for selectively powering the lawn care device based at least in part on operation of an ignition interface controlled by a processor (310), an optical isolator (320) which detect the operational presence of the processor (310) and a shutdown circuit (300) which is able to ground out the ignition coil (360) as a function of the conductive state of the optical isolator (320); the shutdown circuit being powered by an ignition coil (360) of the ignition system to generate a failsafe condition in response to failure or loss of the processor (310).

A fuel vapor system for a vehicle includes a fuel vapor canister that traps fuel vapor from a fuel tank of the vehicle. A purge valve opens to allow fuel vapor flow to an intake system of an engine and closes to prevent fuel vapor flow to the intake system of the engine. An electrical pump pumps fuel vapor from the fuel vapor canister to the purge valve. A diagnostic module (a) selectively diagnoses a fault in the fuel vapor system based on at least one of: (i) a speed of the electrical pump measured using a pump speed sensor; and (ii) a pressure at a location between the electrical pump and the purge valve, and (b) illuminates a malfunction indicator lamp (MIL) within a passenger cabin of the vehicle when the fault is diagnosed.

Methods and systems are provided for diagnosing a humidity sensor positioned in an intake system of a vehicle engine system. In one example, a method comprises rotating an engine unfueled in reverse and injecting a fluid into an exhaust system of the engine system, to draw the fluid into the intake system, where a humidity sensor output signal greater than a baseline output signal by a predetermined threshold is indicative of a humidity sensor that is functioning as desired. In this way, a humidity sensor may be periodically rationalized which may prolong engine lifetime by ensuring the engine is operating at optimal parameters.

Methods and systems are provided for a diagnostic of a humidity sensor positioned in an intake of an engine and adjusting engine operation responsive to findings of the diagnostic. In one example, the method may include sealing a vehicle exhaust system of an engine, combusting fuel at cylinders of the engine while flowing gases through the engine in a first direction, and then, flowing the combusted exhaust gases through the engine in a reverse, second direction to the humidity sensor positioned in the intake. The method may further include indicating degradation of the humidity sensor based on the output of the humidity sensor while flowing gases in the first and second directions.

A method for controlling stabilization of an exhaust gas recirculation (EGR) gas supply may include executing an intake detector condensation stuck resolving mode including, when output abnormality of an intake detector provided at an intake manifold and a variation amount of an EGR rate of an EGR system are detected by a controller while the EGR system is operated, stopping an operation of an EGR valve of the EGR system and then re-operating the EGR valve to resolve abnormality of the intake detector, which is caused by condensation of the EGR gas which is supplied to the intake manifold.

A coolant temperature sensor abnormality determination device includes a determination unit configured to determine whether or not two coolant temperature sensors, which are configured to detect the temperature of the coolant, have an abnormality. The determination unit has a determination permission condition under which a reference temperature is set to an estimated temperature of a present time point and the estimated temperature is then changed from the reference temperature by a determination temperature. The determination unit is configured to determine, when the determination permission condition is satisfied, that the two coolant temperature sensors are functioning normally if a discrepancy between detection values of the two coolant temperature sensors is less than a normal temperature that is less than or equal to the determination temperature.

Methods and systems are provided for diagnosing a humidity sensor positioned in an intake system of a vehicle engine system. In one example, a method comprises rotating an engine unfueled in reverse and injecting a fluid into an exhaust system of the engine system, to draw the fluid into the intake system, where a humidity sensor output signal greater than a baseline output signal by a predetermined threshold is indicative of a humidity sensor that is functioning as desired. In this way, a humidity sensor may be periodically rationalized which may prolong engine lifetime by ensuring the engine is operating at optimal parameters.

A control system includes: an engine; a first hydraulic pump and a second hydraulic pump driven by the engine; a switching device provided in a flow path that connects the first hydraulic pump to the second hydraulic pump, and configured to perform switching between a merged state in which the flow path is opened and a separated state in which the flow path is closed; a first hydraulic actuator to which hydraulic fluid discharged from the first hydraulic pump is supplied in the separated state; a second hydraulic actuator to which hydraulic fluid discharged from the second hydraulic pump is supplied in the separated state; a determining unit configured to determine whether output of the engine is limited; and a merging-separating control unit configured to control the switching device so as to perform switching to the merged state when the determining unit determines that output of the engine is limited.

A method of managing the thermal output of a gas combustion engine having a plurality of combustion zones uses a temperature control system integrated with the engine to provide digital thermal signals to a control unit. The control unit determines when to adjust an engine operating parameter based on an analysis of the thermal signals. The temperature control system includes a plurality of smart thermal sensors with at least one sensor for each combustion zone, a communication bus, and a control unit. Each smart thermal sensor converts the measured temperature from an analog thermal signal to a digital thermal signal.