A method is disclosed for diagnosing the reliability of a pressure sensor disposed in a fuel rail of an internal combustion engine. A control cycle is executed to measure a value of a fuel rail pressure with the pressure sensor, determine a first and a second threshold value of the fuel rail pressure, identify the measured value of the fuel rail pressure as reliable when the measured value is inside an interval of values ranging from the first threshold value to the second threshold value, and identify the measured value of the fuel rail pressure as unreliable when the measured value is outside that interval. The first and the second threshold values may be determined on the basis of a last reliable value of the fuel rail pressure.

Methods and systems are provided for leveraging the pressure dependency of an oxygen sensor for estimating an engine ambient pressure. An intake or exhaust oxygen sensor is used for ambient pressure estimation by applying a reference voltage to the sensor while the engine is being pulled-down in a hybrid vehicle, and correcting an output of the sensor for dilution effects due to ambient humidity. The estimated ambient pressure is used to correct or confirm pressure estimated by other sources, such as other pressure sensors or a pressure model, as well as to tune the performance of the engine.

Methods and systems are provided for conducting a fuel tank pressure transducer rationality test diagnostic procedure in vehicles with sealed fuel tanks. In one example, vehicle-to-vehicle (V2V) or vehicle-to-infrastructure-to-vehicle (V2I2V) technology may be utilized to obtain fuel tank pressure transducer data from a select crowd of vehicles, where the select crowd may be based on the vehicles in the select crowd experiencing similar ambient temperature and weather as the vehicle being diagnosed. In this way, FTPT data from vehicles in the select crowd may be compared to FTPT data in the vehicle being diagnosed, in order to indicate whether the FTPT in the vehicle being diagnosed is functioning as desired, where such a diagnostic can be performed without unsealing the fuel tank on either the vehicle being diagnosed or the vehicles in the select crowd, and which may thus reduce undesired evaporative emissions.

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.

Water-temperature sensors for detection of temperature of cooling water 12 having passed through an engine 1 are increased in number into two (18 and 19). A controller 20 is provided to confirm that each of detection values of the water-temperature sensors 18 and 19 is within a normal range and then employ either of the detection values as temperature of the cooling water 12. The controller 20 is configured such that, when either of the detection values of the water-temperature sensors 18 and 19 is out of the normal range, the remaining detection value within the normal range is employed as temperature of the cooling water 12.

Methods and systems are provided for determining engine knock sensor degradation. In one example, a method may include sending an excitation signal to an actuator to generate vibrations in the absence of engine combustion, and determining engine knock sensor degradation by comparing the knock sensor output with the excitation signal.

Methods and systems are provided for diagnosing sensors in an engine intake by utilizing in an evaporative leak check module pump (ELCM pump). In one example, during engine off conditions, the ELCM pump in an evaporative emission system of the vehicle may be operated in a pressure mode to flow ambient air from the evaporative emissions system to the intake manifold. During humidity sensor diagnostics, the air flow may be used to generate water vapors within the intake manifold, and humidity sensor may be rationalized by monitoring an output of the humidity sensor; and during MAF sensor diagnostics, MAF sensor may be rationalized by monitoring if the MAF sensor output corresponds to a flow rate generated by the ELCM.

The internal combustion engine includes at least one cylinder, an exhaust gas tract having a measuring device, and a tank ventilation system having a purge air line, which provides pneumatic communication between the tank ventilation system and the cylinder. The purge air line has a sensor for ascertaining a hydrocarbon content of a gas flow from the tank ventilation system to the at least one cylinder. Fuel metering into the cylinder is controlled dependent on the ascertained hydrocarbon content. An exhaust gas characteristic of an exhaust gas flow that flows in the exhaust gas tract is detected by the measuring device and compared with a specified target value. If the ascertained difference between the detected exhaust gas characteristic and the specified target value exceeds a specified threshold, a test is carried out to determine whether the sensor has a malfunction.

A method for monitoring an exhaust-gas sensor in which it is determined whether at least one monitored event has occurred by evaluating at least one heat quantity supplied to and/or withdrawn from the exhaust-gas sensor during a period of time, in particular under consideration of a change in the heat quantity stored by the exhaust-gas sensor that occurs during the period of time.

Methods and systems are provided for conducting a canister purging operation and for rationalizing components of a vehicle evaporative emission system. In one example, after completion of a refueling event, a first fuel vapor canister purge operation is conducted to desorb hydrocarbon light ends from the fuel vapor canister, and subsequently the canister is heated to desorb hydrocarbon heavy ends from the canister, which are routed to a hydrocarbon sensor to rationalize the hydrocarbon sensor, before being purged to engine intake in a second purging operation. In this way, a fuel vapor storage canister may be thoroughly cleaned of hydrocarbon light ends and hydrocarbon heavy ends, while additionally indicating whether a canister heating element, and a hydrocarbon sensor positioned between the canister and atmosphere, are functioning as desired.