Fuel Tank Pressure Sensor Diagnosis Using Oxygen Sensor Feedback
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Solution Overview
Problem
Fuel tank pressure sensors may output incorrect readings, leading to insufficient purging of fuel vapors and increased evaporative emissions, as they can fail to indicate pressure changes even when the pressure is out of range, causing inefficiencies in the vehicle's emissions system.
Innovation Solution
A system that evaluates the operation of the fuel tank pressure sensor using the output of an oxygen sensor to diagnose its functionality, distinguishing between sensor degradation and canister purge valve issues, and adjusting the evaporative emissions system accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the fuel tank pressure sensor is used to monitor pressure in the fuel tank, then pressure monitoring is provided, but the sensor may output incorrect readings when degraded leading to insufficient purging and increased emissions
Solution Approach 1:
The system uses feedback from the oxygen sensor to verify the accuracy of the pressure sensor readings. When the oxygen sensor detects fuel vapor in the intake manifold during engine rotation without fueling, this confirms that the pressure sensor is accurately detecting pressure changes in the fuel tank, creating a cross-validation feedback mechanism that resolves the contradiction between measurement precision and reliability
Solution Approach 2:
The oxygen sensor acts as an intermediary device to indirectly verify the pressure sensor's functionality. Instead of directly testing the pressure sensor, the system uses the oxygen sensor's detection of fuel vapor as a mediator to confirm whether the pressure sensor is properly detecting pressure changes, thereby resolving the reliability issue without adding direct testing hardware
2Object-generated harmful factors
If the canister purge valve is opened to purge fuel vapors, then emissions are reduced, but if the pressure sensor is degraded the purging may be insufficient leading to increased evaporative emissions
Solution Approach 1:
The system implements feedback control by using oxygen sensor data to verify whether purging is effectively reducing evaporative emissions. When the oxygen sensor detects rich conditions indicating fuel vapor presence, the system can determine that the purging system is not functioning properly, allowing for corrective action to be taken
Solution Approach 2:
The system performs preliminary diagnostics by rotating the engine without fueling before attempting to purge, allowing the oxygen sensor to detect the presence of fuel vapor in advance. This preliminary action enables the system to identify pressure sensor degradation before it causes significant emissions problems
3Reliability
If the engine is rotated without fueling to diagnose the pressure sensor, then sensor functionality can be evaluated using oxygen sensor output, but this requires specific operating conditions
Solution Approach 1:
The system performs self-diagnosis by automatically rotating the engine without fueling and evaluating the pressure sensor using the oxygen sensor's output. The controller autonomously carries out the diagnostic procedure without requiring external intervention, making the system self-testing while maintaining diagnostic accuracy through the oxygen sensor feedback mechanism
Data Source
AI summary
Methods and systems are presented for diagnosing operation of a fuel tank pressure sensor. The methods and systems may include releasing fuel vapors from a fuel tank to an engine when an engine is rotating in a fuel cut out mode while a catalyst temperature is greater than a threshold temperature to determine whether or not the fuel tank pressure sensor is degraded.