Abstract: A loose or missing fuel cap detection method for an evaporative emission control system of an automotive vehicle detects a loose or missing fuel cap based in part on whether fuel level changed. The method determines whether the fuel level changed, which is indicative of a refueling event. The method then determines if one or more leaks are present. If the fuel level changed and one or more leaks are present, the method determines that the fuel cap is loose or missing.

Abstract: A diagnostic method for an evaporative emission control system of an automotive vehicle determines functionality of one of a purge valve and/or a vacuum switch and valve assembly. The vacuum switch and valve assembly is located between a carbon canister and atmosphere and is either open or closed according to whether the system is in a high or low negative pressure condition. A controller determines if the vacuum switch and valve assembly is functioning properly according to the high or low negative pressure condition. The controller determines if the purge valve is functioning properly based on engine performance characteristics.

Abstract: In a motor vehicle having an engine with an exhaust catalyst and an oxygen sensor upstream of the catalyst and an oxygen sensor downstream of the catalyst, a method for detecting whether the catalyst has aged. Over a test block period of time, the method periodically obtains upstream data points from an oxygen sensor located upstream of the catalyst and from and oxygen sensor located downstream of the catalyst. Absolute differences are calculated between consecutive pairs of the upstream data points and the downstream data points. A ratio between the sums of absolute differences is then calculated, and the ratio is used to determine whether the catalyst has aged.

Abstract: A non-intrusive method and arrangement for detecting the aging of an oxygen sensor, without increasing tailpipe emissions, is provided. The method detects an aging oxygen sensor, located between a motor vehicle engine and a catalytic converter, by sampling a series of oxygen level signals taken over a calibratable time block only when at least one engine operating condition satisfies a predetermined criterion whereunder the method will not intrude upon the engine controller's ability to minimize undesirable exhaust emissions. After a series of signal processing, the samplings are then compared to calibratable thresholds in order to determine the aging degree of the oxygen sensor.

Abstract: A non-intrusive method and arrangement for detecting the aging of an oxygen sensor, without increasing tailpipe emissions, is provided. The method detects an aging oxygen sensor, located between a motor vehicle engine and a catalytic converter, by sampling a series of oxygen level signals taken over a calibratable time block only when at least one engine operating condition. satisfies a predetermined criterion whereunder the method will not intrude upon the engine controller's ability to minimize undesirable exhaust emissions. After a series of signal processing, the samplings are then compared to calibratable thresholds in order to determine the aging degree of the oxygen sensor.

Abstract: In a motor vehicle having an engine with an exhaust catalyst and an oxygen sensor upstream of the catalyst and an oxygen sensor downstream of the catalyst, a method for detecting whether the catalyst has aged. Over a test block period of time, the method periodically obtains upstream data points from an oxygen sensor located upstream of the catalyst and from and oxygen sensor located downstream of the catalyst. Absolute differences are calculated between consecutive pairs of the upstream data points and the downstream data points. A ratio between the sums of absolute differences is then calculated, and the ratio is used to determine whether the catalyst has aged.

Abstract: A method is provided for detecting a small or gross leak in an evaporative emission control system of an automotive vehicle. The method includes initially purging and then sealing the evaporative emission control system. A vacuum switch coupled to the evaporative emission control system is then monitored for an opening event caused by a loss of a natural vacuum created in the evaporative emission control system. If said opening event is detected, the method determines if a leak check timer has exceeded a first or second predetermined threshold value. If the leak check timer has not exceeded said first predetermined threshold value a first fault code is set indicating that the gross leak has been detected. If the leak check timer has not exceeded the second predetermined threshold value, a second fault code is set indicating that the small leak has been detected. The first threshold value corresponds to an amount of time required for a leak to be detected having a diameter of about 0.070 inches or greater.

Abstract: A method is provided for cleansing a seal of a device used for sealing an evaporative emission control system of an automotive vehicle. The method starts by determining if a request to close the device has been made. If the request to close the device has been made, the method cycles the device a plurality of times to press and lift the seal off of a seat repeatedly. The method also determines if the seal is closed after the cycling step. If the seal is not closed after the cycling step, the method closes the seal. Preferably, the cycling step includes cycling the device at a pre-selected duty cycle, frequency and cycle count. The duty cycle, frequency, and cycle count correspond to calibration tables prepared for the particular device employed to insure that the seal strikes its seat about three times before sealing.

Abstract: A method is provided for determining the rationality of a device for monitoring the pressure within an evaporative emission control system of an automotive vehicle. The method includes opening a valve of the evaporative emission control system and determining if a vacuum switch of the evaporative emission control system opened. If the vacuum switch opened, a code is set indicating that the vacuum switch passed an opening test. If the vacuum switch did not open, the method determines if a fail timer is greater than a first fail threshold value. The first fail threshold value corresponds to an amount of time within which a properly functioning vacuum switch should open after said valve is opened. If the fail timer is greater than the fail threshold value, the method sets a code indicating that the vacuum switch failed the opening test. If the fail timer is less than or equal to the first fail threshold value, the method increments the fail timer.

Abstract: A method is provided for detecting a small or gross leak in an evaporative emission control system of an automotive vehicle. The method includes initially purging and then sealing the evaporative emission control system. A vacuum switch coupled to the evaporative emission control system is then monitored for an opening event caused by a loss of a natural vacuum created in the evaporative emission control system. If said opening event is detected, the method determines if a leak check timer has exceeded a first or second predetermined threshold value. If the leak check timer has not exceeded said first predetermined threshold value a first fault code is set indicating that the small leak has been detected. If the leak check timer has not exceeded the second predetermined threshold value, a second fault code is set indicating that the small gross leak has been detected. The first threshold value corresponds to an amount of time required for a leak to be detected having a diameter of about 0.

Abstract: A method is provided for detecting a very small leak in an evaporative emission control system of an automotive vehicle. The method includes sealing the evaporative emission control system at a key-off event and monitoring a vacuum switch coupled to the evaporative emission control system for a closing event due to a natural vacuum created in the evaporative emission control system as it cools. If the closing event is not detected, the method determines if a leak detection timer has exceeded a predetermined threshold value. If the timer has exceeded the predetermined threshold value, the method sets a fault code indicating that the very small leak has been detected.

Abstract: A computerized method diagnoses a vehicle temperature sensor. The method includes the steps of verifying a fault status for the sensor, and initializing a mileage based diagnostic when the default status indicates that no sensor faults are present. The mileage based diagnostic is conducted on the sensor upon initialization. The mileage based diagnostic is conducted by calculating a change in temperature and comparing the change in temperature to a predetermined temperature change. A change in mileage is also calculated and compared to a predetermined mileage change. The mileage based diagnostic further includes comparing a number of warmups for the vehicle to a predetermined number of warmups. The sensor is failed when the change in mileage reaches the predetermined mileage change, the number of warmups reaches the predetermined number of warmups, and the change in temperature does not reach the predetermined temperature change.