The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality.
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The control module 70 executes the fuel level detection cross-check control of the present invention. More specifically, one of a plurality of fuel level condition flags is set based on SFL. The fuel level condition flags include, but are not limited to, an empty tank flag (FLAGET), a first switch stuck flag (FLAGS1) (e.g., indicating that the empty switch 50 is stuck in the empty position), a first or second switch stuck flag (FLAGS1,2) (e.g., indicating that either the empty switch 50 is stuck in its uppermost position or the fuel level sensor 40 is stuck in its lowest (i.e., empty) position), a full tank flag (FLAGFT) and a mid-level flag (FLAGML). The flags are set based on the exemplary truth table below:
The control module 70 indicates the fuel level in the secondary fuel tank 28 based on FLAGET, FLAGML or FLAGFT. If FLAGML, in particular, is set, the control module 70 uses a traditional rationality check to determine whether the fuel level sensor 40 is functioning properly. If one of FLAGS1 and FLAGS1,2 are set, the control module 70 sets a diagnostic trouble code (DTC) and illuminates a malfunction indicator lamp (MIL) or other visual or audible device to convey to the vehicle operator that there is a malfunction. Further, because the resistances are added in series, current fuel level reading algorithms are still able to be implemented for fuel level determination and existing in range diagnostics still function correctly.
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In step 408, control determines whether SFL is less than RTHR2 and greater than a third resistance threshold (RTHR3) (e.g., 230 Ohms). If SFL is less than RTHR2 and is greater than RTHR3, one of the empty switch and the fuel level sensor is not functioning properly, control sets FLAGS1,2 in step 410 and control ends. If SFL is not less than RTHR2 and is not greater than RTHR3, control determines whether SFL is less than or equal to RTHR3 and is greater than or equal to a fourth resistance threshold (RTHR4) (e.g., 20 Ohms) in step 412. If SFL is less than or equal to RTHR3 and is greater than or equal to RTHR4, control sets FLAGML in step 414 and control ends. If SFL is not less than or equal to RTHR3 and is not greater than or equal to RTHR4, control sets FLAGFT in step 416 and control ends.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.