Abstract: A diagnostic system for an engine of a vehicle includes a temperature determination module, a comparison module, and a fault indication module. The temperature determination module receives an indication of whether one or more cylinders within the engine are deactivated and selects a first temperature threshold based on the indication. The comparison module selectively determines whether a temperature of engine coolant is less than the first temperature threshold. The fault indication module diagnoses a fault in response to the comparison module determining that the temperature of the engine coolant is less than the first temperature threshold.

Abstract: A selective catalytic reduction (SCR) system includes a first sensor that determines a first concentration of NOx, a second sensor that determines a second concentration of NOx and NH3, and a fault determination module. The fault determination module diagnoses a fault in at least one of a dosing agent and a catalyst in an SCR device based on the first and second concentrations.

Abstract: A system according to the principles of the present disclosure includes an error count module and a sensor diagnostic module. The error count module increases an error count when an actual air/fuel ratio generated by an oxygen sensor monitoring an exhaust system of an engine is different than a desired air/fuel ratio. The error count module selectively adjusts a rate at which the error count is increased based on an ambient temperature. The sensor diagnostic module diagnoses a fault in the oxygen sensor when the error count is greater than a first predetermined count.

Abstract: A diagnostic system of a vehicle includes an impedance module and a diagnostic module. The impedance module determines an impedance of a sensing element of an exhaust gas oxygen sensor based on a response of the sensing element to a change in current through the sensing element. The diagnostic module selectively diagnoses a fault associated with the exhaust gas oxygen sensor based on the impedance of the sensing element.

Abstract: A control system for a selective catalytic reduction (SCR) system includes a dosing control module, a comparison module, and a status determination module. The dosing control module controls a dosing system to inject a desired amount of ammonia into exhaust gas at a first location in an exhaust stream. The comparison module compares a measured amount of ammonia in the exhaust gas to the desired amount of ammonia, wherein the measured amount of ammonia is measured at a second location downstream from the first location and upstream from or within an SCR catalyst. The status determination module determines a pass/fail status of a component of the dosing system based on the comparison between the measured amount of ammonia and the desired amount of ammonia.

Abstract: A system according to the principles of the present disclosure includes a pump control module and a pump diagnostic module. The pump control module commands a water pump to switch between on and off, wherein the water pump circulates coolant through an engine when the water pump switches on as commanded. The pump diagnostic module diagnoses a fault in the water pump based on a change in a crankshaft speed of the engine when the water pump is commanded to switch between on and off.

Abstract: A system according to the principles of the present disclosure includes a diagnostic execution module and a diagnostic disabling module. The diagnostic execution module diagnoses a fault in at least one of an oxygen sensor and a catalytic converter based on input received from the oxygen sensor. The diagnostic disabling module disables the diagnosing based on at least one of a temperature of the catalytic converter and a mass flow rate of air flowing through the catalytic converter.

Abstract: A system according to the principles of the present disclosure includes an error count module and a sensor diagnostic module. The error count module increases an error count when an actual air/fuel ratio is different from a desired air/fuel ratio and selectively adjusts the error count based on an actual engine speed. An oxygen sensor generates a signal indicating the actual air/fuel ratio. The sensor diagnostic module diagnoses a fault in the oxygen sensor when the error count is greater than a first predetermined count.

Abstract: A method and control system for a selective catalytic reduction (SCR) catalytic converter and an ammonia dosing module that stores ammonia in a selective catalyst reducing (SCR) catalyst and that depletes the ammonia level by discontinuing or reducing dosing. The control system also includes an SCR conversion efficiency module that determines an SCR efficiency. An SCR efficiency comparison module compares the SCR efficiency to an efficiency threshold and generates a fault indicator when the SCR efficiency is not above the efficiency threshold.

Abstract: A diagnostic system for a vehicle includes a comparison module, a disabling module, and a fault indication module. The comparison module indicates whether a temperature of engine coolant is less than a first predetermined temperature. The disabling module disables the comparison module until the temperature of the engine coolant is greater than a second predetermined temperature. The fault indication module diagnoses a fault in response to the comparison module indicating that the temperature of the engine coolant is less than the first predetermined temperature.

Abstract: A monitoring module selectively generates a request to at least one of: transition from providing rich fueling an engine to operating the engine in a fuel cutoff (FCO) state; and transition from operating the engine in the FCO state to providing rich fueling to the engine. In response to a response to the request, the monitoring module: selectively controls fueling to the engine to perform the at least one of the transitions; and selectively determines whether a fault is present in a component based on a response to the at least one of the transitions. A hybrid control module controls an electric motor of the hybrid vehicle and that selectively generates the response.

Abstract: A system according to the principles of the present disclosure includes a pump control module, an actuator control module, and a torque reserve module. The pump control module switches a water pump between on and off. The water pump circulates coolant through an engine when the water pump is on. The actuator control module controls a first actuator of the engine based on a first torque request and that controls a second actuator of the engine based on a second torque request. The torque reserve module adjusts a torque reserve before the water pump is switched on or off based on a change in engine load expected when the water pump is switched on or off. The torque reserve is a difference between the first torque request and the second torque request.

Abstract: A diagnostic system for a vehicle includes an error module, an equivalence ratio (EQR) module, a threshold determination module, and a fault indication module. The error module determines an error value based on a difference between an amount of oxygen in exhaust measured by an exhaust gas oxygen sensor (EGO) upstream of a catalyst and an expected value of the amount. The EQR module selectively controls fuel injection based on the error value. The threshold determination module determines an error threshold based on a flow rate of fuel vapor from a vapor canister to an intake manifold of an engine. The fault indication module selectively indicates that a fault is present in the EGO sensor based on the error value and the error threshold.

Abstract: A system according to the principles of the present disclosure includes an error count module and a sensor diagnostic module. The error count module increases an error count when an actual air/fuel ratio generated by an oxygen sensor monitoring an exhaust system of an engine is different than a desired air/fuel ratio. The error count module selectively adjusts a rate at which the error count is increased based on an ambient temperature. The sensor diagnostic module diagnoses a fault in the oxygen sensor when the error count is greater than a first predetermined count.

Abstract: A diagnostic system for an engine of a vehicle includes a temperature determination module, a comparison module, and a fault indication module. The temperature determination module receives an indication of whether one or more cylinders within the engine are deactivated and selects a first temperature threshold based on the indication. The comparison module selectively determines whether a temperature of engine coolant is less than the first temperature threshold. The fault indication module diagnoses a fault in response to the comparison module determining that the temperature of the engine coolant is less than the first temperature threshold.

Abstract: A system according to the principles of the present disclosure includes an error period module and a sensor diagnostic module. The error period module determines an error period based on an amount of time that a first air/fuel ratio and a desired air/fuel ratio are different. A first oxygen sensor generates a first signal indicating the first air/fuel ratio. The sensor diagnostic module diagnoses a fault in the first oxygen sensor when the error period is greater than a predetermined period.

Abstract: An internal combustion engine operating at a lean air/fuel ratio includes a reductant injection system configured to dispense reductant into an exhaust gas feedstream upstream of a selective catalytic reduction device. The reductant injection system includes a reductant delivery system fluidly coupled to a reductant dispensing device that is configured to dispense the reductant. A method for monitoring the reductant injection system includes commanding the reductant dispensing device to dispense reductant at a prescribed reductant flowrate, controlling the reductant delivery system to a preferred operating state, monitoring operation of the reductant delivery system and estimating a reductant flowrate as a function of the monitored operation of the reductant delivery system, and diagnosing operation of the reductant injection system as a function of the prescribed reductant flowrate and the estimated reductant flowrate.

Abstract: An apparatus and method of controlling a vehicle aftertreatment system is provided. The aftertreatment system treats exhaust gas produced by the vehicle engine and includes a particulate filter, and a NOx reducing device such as a selective catalytic reduction (SCR) device. The particulate filter is configured to regenerate to remove accumulated particles when the exhaust gas is heated above a regeneration temperature. A diagnostic device is included for monitoring the aftertreatment system. The diagnostic device may be a sensor for measuring the oxides of nitrogen (NOx) and/or an SCR efficiency monitor. A controller is employed to optimize the function of the diagnostic device. The controller does not enable the diagnostic device when the vehicle is powered until one or more entry conditions are satisfied.

Abstract: An exhaust diagnostic system comprises a selective catalyst reduction (SCR) component testing module, an exhaust stream temperature management module, and a test enabling module. The component testing module executes an SCR component efficiency test. The exhaust stream temperature management module adjusts a temperature of the SCR component to a predetermined temperature range. The test enabling module executes a process for depleting a reductant load and subsequently initiates an SCR component efficiency test while the temperature of the SCR catalyst is within the predetermined temperature range. A method for diagnosing an exhaust system comprises determining an efficiency of an SCR component and selectively adjusting a temperature of the SCR component to a predetermined temperature range. The method also includes executing a process for depleting a reductant load and initiating an SCR component efficiency test while the temperature of the SCR component is within the predetermined temperature range.

Abstract: An exhaust diagnostic control system comprises a test enabling module, an exhaust gas temperature management module, and an exhaust diagnostic control system. The test enabling module is configured for executing a process for depleting a reductant load and subsequently establishing a known concentration of reductant on an after-treatment component following an occurrence of one or more trigger events. The exhaust gas temperature management module is configured for selectively adjusting a temperature of the after-treatment component to a predetermined temperature range using intrusive exhaust gas temperature management. The component management module is configured for executing a NOx reduction efficiency test following completion of the process for depleting a reductant load and subsequently establishing a known concentration of reductant on the after-treatment component. The NOx reduction efficiency test comprises determining a NOx reduction efficiency associated with the after-treatment component.