Abstract: A vehicle includes an internal combustion engine having a plurality of cylinders, a sensor configured to generate a sensor signal correlated with an air-fuel ratio of first and second cylinders of the plurality of cylinders, and a controller in communication with the sensor and programmed to monitor the air-fuel ratio of the first cylinder in response to an indication that air-fuel ratio measurements of the first cylinder satisfy predetermined criteria for current engine operating conditions while air-fuel ratio measurements of the second cylinder do not satisfy the predetermined criteria for the current engine operating conditions.

Abstract: Methods and systems are provided for diagnostics of exhaust gas recirculation (EGR) components including an EGR pressure sensor. In one example, a method may include comparing a current relationship between an output of the EGR pressure sensor and a manifold air pressure (MAP) and a pre-calibrated relation between the output of the EGR pressure sensor and the MAP to detect degradation of the EGR pressure sensor.

Abstract: Methods and systems are provided for a coolant system. In one example, a method may include diagnosing a condition of a pump of the coolant system based on a temperature change of coolant. The diagnostic may determine if the pump is stuck on or off.

Abstract: Methods and systems are provided for diagnostics of exhaust gas recirculation (EGR) components including an EGR pressure sensor. In one example, a method may include comparing a current relationship between an output of the EGR pressure sensor and a manifold air pressure (MAP) and a pre-calibrated relation between the output of the EGR pressure sensor and the MAP to detect degradation of the EGR pressure sensor.

Abstract: Methods and systems are provided for a high-pressure exhaust gas recirculation system. In one example, the high-pressure exhaust gas recirculation system comprises pressure seconds arranged on different sides of a valve. The pressure sensors are used to regulate exhaust-gas recirculate flow without a fixed orifice delta pressure sensor.

Abstract: Methods and systems are provided for a vehicle coolant circuit. In one example, the coolant circuit includes a heater core isolation valve (HCIV) where a status of the HCIV may be diagnosed by intrusively activating a positive temperature coefficient heater in a cooling loop in which the HCIV is arranged. A response of coolant temperature to heater activation may be used to determine a position of the HCIV.

Abstract: Methods and systems are provided for monitoring a status of a heater core isolation valve (HCIV) housing in an engine coolant circuit including a first coolant loop and a second coolant loop. In one example, a method may include indicating degradation of the HCIV based on a difference between a first coolant loop temperature and a second coolant loop temperature upon activation of coolant system pumps and deactivation of a positive temperature coefficient (PTC) heater housed in the cabin heating loop.

Abstract: Methods and systems are provided for a high-pressure exhaust gas recirculation system. In one example, the high-pressure exhaust gas recirculation system comprises pressure seconds arranged on different sides of a valve. The pressure sensors are used to regulate exhaust-gas recirculate flow without a fixed orifice delta pressure sensor.

Abstract: Methods and systems are provided for a high-pressure exhaust gas recirculation system. In one example, the high-pressure exhaust gas recirculation system comprises pressure sensors arranged on different sides of an EGR valve. Feedback from the pressure sensors are used to diagnose a EGR valve position sensor.

Abstract: Methods and systems are provided for operating a vehicle that includes an exhaust gas heat recovery device having an exhaust heat recovery device valve that may be selectively opened and closed. In one example, a method may include storing heat from exhaust gases in a phase changing material and releasing the stored heat to surroundings of an exhaust heat recovery device valve to reduce a possibility of the exhaust heat recovery device valve sticking.

Abstract: Methods and systems are provided for monitoring a status of a heater core isolation valve (HCIV) housing in an engine coolant circuit including a first coolant loop and a second coolant loop. In one example, a method may include indicating degradation of the HCIV based on a difference between a first coolant loop temperature and a second coolant loop temperature upon activation of coolant system pumps and deactivation of a positive temperature coefficient (PTC) heater housed in the cabin heating loop.

Abstract: Methods and systems are provided for a vehicle coolant circuit. In one example, the coolant circuit includes a heater core isolation valve (HCIV) where a status of the HCIV may be diagnosed by intrusively activating a positive temperature coefficient heater in a cooling loop in which the HCIV is arranged. A response of coolant temperature to heater activation may be used to determine a position of the HCIV.

Abstract: Methods and systems are provided for on-board diagnostics of components of an exhaust gas heat recovery (EGHR) system including engine coolant temperature sensors coupled to the system. Degradation of one or more of a first coolant temperature sensor coupled upstream of a heat exchanger of the EGHR system and a second coolant temperature sensor coupled downstream of the heat exchanger may be indicated based on a difference between a modeled coolant temperature and a measured coolant temperature, the modeled coolant temperature based on one or more of heat transfer between a heater core and vehicle cabin, and heat transfer between exhaust flowing via the heat exchanger and coolant flowing through the heat exchanger.

Abstract: Methods and systems are provided for controlling coolant flow through parallel branches of a coolant circuit including an AC condenser and a charge air cooler. Flow is apportioned responsive to an AC head pressure and a CAC temperature to reduce parasitic losses and improve fuel economy. The flow is apportioned via adjustments to a coolant pump output and a proportioning valve.

Abstract: Methods and systems are provided for on-board diagnostics of components of an exhaust gas heat recovery (EGHR) system including engine coolant temperature sensors coupled to the system. Degradation of one or more of a first coolant temperature sensor coupled upstream of a heat exchanger of the EGHR system and a second coolant temperature sensor coupled downstream of the heat exchanger may be indicated based on a difference between a modeled coolant temperature and a measured coolant temperature, the modeled coolant temperature based on one or more of heat transfer between a heater core and vehicle cabin, and heat transfer between exhaust flowing via the heat exchanger and coolant flowing through the heat exchanger.

Abstract: Methods are provided for engine coolant system diagnostics. In one example, engine coolant system malfunction is indicated based on an engine coolant temperature inference model, whereas in another example engine coolant system malfunction is indicated based on a time-based monitor, where the inference model is enabled at ambient temperatures above a predetermined threshold, and where the time-based monitor is enabled at ambient temperatures below the predetermined threshold. In this way, accurate engine coolant system diagnosis may be accomplished under ambient temperature conditions wherein the engine coolant temperature inference model may be compromised.

Abstract: Methods and systems are provided for controlling coolant flow through parallel branches of a coolant circuit including an AC condenser and a charge air cooler. Flow is apportioned responsive to an AC head pressure and a CAC temperature to reduce parasitic losses and improve fuel economy. The flow is apportioned via adjustments to a coolant pump output and a proportioning valve.

Abstract: Methods are provided for engine coolant system diagnostics. In one example, engine coolant system malfunction is indicated based on an engine coolant temperature inference model, whereas in another example engine coolant system malfunction is indicated based on a time-based monitor, where the inference model is enabled at ambient temperatures above a predetermined threshold, and where the time-based monitor is enabled at ambient temperatures below the predetermined threshold. In this way, accurate engine coolant system diagnosis may be accomplished under ambient temperature conditions wherein the engine coolant temperature inference model may be compromised.