BACKGROUND OF INVENTION 
     The present invention relates generally to a method and system for operating a motor vehicle. More particularly, the invention relates to a controller-assisted method and system for starting a motor vehicle. 
     Conventional motor vehicle starting systems include so-called “four-position” ignition key switches having one or more OFF or “lock” positions, an ACC (“accessories”) position, a RUN position, and a START position. With the exception of alarm systems, clocks and mobile phones, most onboard electrical systems and components are typically disabled when the ignition switch is in the OFF position. When in the ACC position, designated vehicle accessories, such as a radio, power windows and the like, are activated via the vehicle&#39;s electrical system. When in the RUN position, typically all onboard electrical systems, including the vehicle&#39;s powertrain control module, are activated. 
     Typically, in order to start or “crank” the engine, a conventional ignition switch must be turned to the START position and held there until the engine is successfully started. However, if the key is not held in the START position for a long enough period of time, a spring mechanism provided inside the switch will force the key back to the RUN position thus removing power from the starter solenoid and disengaging the starter motor. Uneventful cranking often depends on an operator&#39;s ability to properly turn and maintain the switch in the START position for a required period of time. 
     Early release of the ignition switch from the START position can result in undesirable operating states of the internal combustion engine, including for example misstarts and reverse running of the engine. Repeated misstarts for example may damage the vehicle starter and reduce its longevity, and also effect a customer&#39;s satisfaction with the vehicle. Misstarts may also increase vehicle exhaust emissions during vehicle cold start conditions. To address such problems, three-position mechanical ignition switches have been developed to reduce the level of effort required by an operator to turn and maintain the ignition switch in the proper position. See for example U.S. Pat. No. 5,936,316 having a combined RUN/START and no integral return spring. 
     Conventional starting systems however are also characterized by crank delays inherent in the vehicle start-up process itself. These delays are especially noticeable in vehicles having passive anti-theft systems (PATS) wherein a certain amount of time is required for key verification. Depending on the algorithms used and the number of previously unsuccessful verification attempts, the overall vehicle crank delay time is increased. Add to this the time required for other start-up processes, such as fuel pump priming, and the overall crank delay time is further increased. 
     Accordingly, the inventors have recognized a need for an improved vehicle starting system that minimizes overall vehicle crank times and provides an improved “touch” feel to the vehicle starting process. 
     SUMMARY OF INVENTION 
     The aforedescribed limitations of conventional automobile starting systems are substantially overcome by the present invention, in which a method is provided for crank-starting a motor vehicle having an internal combustion engine, an operator actuatable switch, an electric starter and a corresponding starter relay. The method includes the steps of coupling the starter relay to a first circuit during one or more crank operations and coupling the starter relay to a second circuit during the one or more crank operations. Preferably, the first circuit is coupled to the high-side of the starter relay and the second circuit is coupled to the low-side of the starter relay. Crank operations include for example fuel pump priming and vehicle key verification. 
     An advantage of the present invention is that the overall crank delay of a vehicle&#39;s starting system can be minimized by providing both high-side and low-side control of the starter relay. For example, vehicle key verification can be performed simultaneously with other vehicle start-up functions such as fuel pump priming. The dual control strategy also serves to eliminate single point failures that may lead to inadvertent start-up of the vehicle. 
     The claimed invention has an additional advantage of improving the “feel” of the engine start-up process by providing a “touch” quality or sensitivity to a conventional vehicle ignition switch. This is realized both by a shorter crank delay time, and by controller logic that automatically triggers control of the crank process when the ignition switch is in the “start” position. In accordance with the present invention, the electronic controller assumes control of the start-up functions even when the operator misstarts the vehicle by prematurely and unintentionally releasing the ignition switch. The operator however is still able to override the starting process by turning the ignition switch to the OFF or ACC positions. The present invention thus has the further advantage of improving customer satisfaction by minimizing misstart occurrences due to premature and unintentional disengagement of the ignition switch from the “start” position. 
     Still further, by minimizing misstart occurrences, cold start emissions caused by manifold fuel loading are reduced. Also, by preventing re-engagement and over-engagement of the starter motor in accordance with the present invention, starter motor and flywheel longevity can be increased. 
     In a related aspect of the invention, a vehicle starting system is provided having a starter motor coupled to a battery via a starter relay and an operator actuatable ignition switch. The system includes a first control circuit coupled to a high-side of the starter relay, a second control circuit coupled to a low-side of the starter relay, and an electronic controller coupled to the first and second circuits for providing high-side and low-side control signals, respectively, to the first and second control circuits when the ignition switch is turned to the start position. 
     Further advantages, objects and features of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying figures showing illustrative embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     For a complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein: 
     FIG. 1 is a block diagram of a vehicle starting system in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a detailed schematic diagram of a vehicle starting system in accordance with the preferred embodiment of FIG. 1; 
     FIG. 3 is a flow diagram of a preferred method for starting a motor vehicle in accordance with the present invention; and 
     FIG. 4 is a detailed flow diagram of the vehicle starting method of FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a block diagram of a vehicle starting system  100  in accordance with a preferred embodiment of the present invention. As shown in FIG. 1, the system includes a starter motor  150  coupled to a battery or equivalent storage device  160  via a starter relay  130 . The starter relay  130  includes a “high-side  132 ” at a first potential, and a “low-side”  134  at a second potential. Preferably, the “high-side”  132  of the relay is at a higher potential than the “low-side”  134  of the relay, but the invention is not so limited. When engaged via an operator actuatable switch, shown for example as  208  in FIG. 2, the starter relay is activated and electrical power is provided from the battery  160  to various vehicle components, including the starter motor  150 , for vehicle start-up. As known in the art, the operator actuatable switch is preferably a four-position ignition key switch having at least one OFF or lock position, an ACC position, a RUN position and a START position. 
     Referring again to FIG. 1, an electronic controller  110  is provided for implementing the vehicle start-up methods of FIGS. 3 and 4 discussed below. The controller  110 , which can be any suitable powertrain controller or suitable powertrain controller or microprocessor-based module, provides both a high-side control signal to a high-side control circuit  120  and a low-side control signal to a low-side control circuit  140  when the controller senses the ignition switch in the START position. Nominally, the controller  110  includes a central processing unit (CPU), a data bus of any suitable configuration, corresponding input/output ports, random-access memory (RAM), keep-alive memory (KAM) and read-only memory (ROM) or equivalent electronic storage medium  146  containing processor-executable instructions and database values for controlling engine operation in accordance with FIGS. 3 and 4. The controller  110  receives various signals from conventional vehicle sensors, the sensors including but not being limited to an engine speed sensor and an engine temperature sensor. The speed and temperature sensors are shown by way of example as sensors  204  and  206 , respectively, in FIG.  2 . 
     FIG. 2 shows a detailed schematic diagram of a vehicle starting system in accordance with the preferred embodiment of FIG.  1 . The system includes a high-side control circuit  120  and a low-side control circuit  140 . The high-side control circuit  120  includes a first high-side relay  212  activatable via a high-side control signal (“Crank Request”) for providing electrical power to the high-side of a starter relay  130 . The crank request provides a ground for the first and second high-side relays  212  and  214 . Thus, when commanded, the relay  214  switches from a normally closed (NC) position to a closed R 1  position and electrical power is provided for “START” and related functions. Relay  214 , which is normally closed in the R 2  position, is commanded via a crank request signal to disable vehicle ACC and RUN functions and enable vehicle START and related functions. Absent the crank request signal, the first high-side relay  212  is configured to enable RUN or START functions depending on the position of the ignition switch, and the second high-side relay configured to enable RUN or ACC functions. 
     The relay devices shown in FIG. 2, for example relays  212 ,  214  and  130 , can be any suitable switching devices such as electromechanically-actuated or transistor-based switches. The relays can be embodied in hardware, software or a combination of both. The system of FIG. 2 further includes a transmission status switch  216 , which for example can be a conventional park/neutral (PRNDL) switch, which if appropriately set in a PARK or a NEUTRAL position allows the high-side  132  of the starter relay  130  to be energized. Switch  216  also can be embodied in hardware and/or software and coupled to the electronic controller  110 . 
     Regarding the low-side control of the starter relay  130 , when a key  209  is inserted in the ignition switch  208 , the controller  110  provides a key verification signal to a passive anti-theft system (PATS) module  222  via a communications link  250 . The PATS module  222  can be part of the electronic controller  110 , or separate as shown in FIG.  2 . Preferably, the communications link  250  allows the forwarding of data messages to and from the PATS module  222 . 
     If the PATS signal is accepted, the PATS module  222  will ground the low side of the starter. When the key is turned from the RUN to the START (crank) position, the controller checks the engine speed (RPM) and engine/coolant temperature. If RPM is below a threshold level, the controller provides a ground for the low side of a series of relays, which in turn removes current from systems that are not necessary during the crank process. If the vehicle is in PARK or NEUTRAL, current is then supplied to the high side of the starter relay thus engaging the starter. 
     FIG. 3 shows a flow diagram of a preferred method for starting a motor vehicle in accordance with the present invention. The method, which is implemented for example by the foregoing systems of FIGS. 1 and 2, first includes the step of monitoring a vehicle ignition switch and determining whether it is in the START position, step  302 . If the ignition switch is in the START position, the high-side and low-side controls are provided to the starter relay in accordance with steps  304  and  306 . Otherwise, if the ignition switch is not in the START position, then non-start operations are initiated and electrical power is supplied to various vehicle components in accordance with predefined ACC and RUN functions. 
     FIG. 4 shows a detailed flow diagram of the preferred method of FIG.  3 . The method includes the additional steps of engaging or disengaging the starter motor based on engine/coolant temperature. As shown with reference to FIG. 2, the controller  110  checks the position of the ignition switch to determine whether the switch is in either the RUN or START positions, steps  402  and  404 . If the switch is in either of these two positions, then the start control method is terminated. Likewise, if the ignition switch is in the RUN position and a crank request has not yet been received (“Start Engine Request=False”), step  406 , then starter control method is terminated. 
     Otherwise, if the ignition switch is in the START position, step  404 , or if the ignition switch is in the RUN position and a crank request has already been received (“Start Engine Request=True”), steps  402  and  406 , then the controller  110  checks the sensed engine speed (RPM) provided by sensor  204 , step  410 . The controller interrogates the engine RPM and coolant temperature to determine if a sufficient RPM has been achieved in order to disengage the starter. Once such a condition has been achieved, the controller removes the ground from the control relays  212  and  214  thus shutting off the starter and current to related electrical components/functions. The controller then sends a Controller Area Network (CAN) message, or other suitable message, to the PATS module to remove the ground from the starter relay. If the controller determines that the RPM is not zero or greater than a given engine speed threshold (step  410 ), i.e., engine is running, then the crank request is ignored subject to steps  414 ,  416  and  426  discussed below. The engine speed threshold in accordance with step  410  is nominally set to zero. 
     If RPM is zero or alternatively below a predetermined speed threshold value in accordance with step  410 , then the controller sets an “Engine Started Flag” to “False”, disables vehicle ACC functions, and allows high-side and low-side control signals to be applied to the starter relay as described above, step  412 . If however RPM is not zero (or is greater than the engine speed threshold), then the controller compares a sensed engine coolant temperature provided by sensor  206  to a predetermined “warm” engine temperature limit, step  414 . The warm engine temperature limit is calibratable and can be dependent on several factors, including but not limited to the design, specific application and operating conditions of the internal combustion engine. If the engine/coolant temperature exceeds the warm temperature limit, then RPM is compared to a “warm start” RPM limit, step  416 , and then in accordance with step  418 , the “Engine Started Flag” is set to “True”, the starter disabled and ACC functions enabled. The warm start RPM limit is also calibratable and can be dependent on several factors, including but not limited to the design, specific application and operating conditions of the internal combustion engine. A “Start Engine Request” flag is then set to “False” in accordance with step  420  to cancel any previous crank request. 
     If RPM is less than or equal to the warm start RPM limit in accordance with step  416 , then the controller compares the amount of time the “Start Engine Request” has been set to “True” to a predetermined crank time limit, step  424 . The crank time limit is calibratable and can depend on the design, specific application and operating conditions of the internal combustion engine. If the engine has been cranking for period of time less than or equal to the crank time limit, then the “Start Engine Request” flag is set to “False” and starter motor is engaged and ACC functions disabled, step  424 . If however the engine crank exceeds the crank time limit, then the crank operation is terminated. 
     Referring again to step  414 , if however the engine/coolant temperature is less than the warm temperature limit, then RPM is first compared to a “cold start” RPM limit. The cold start RPM limit is calibratable and can depend on the design, specific application and operating conditions of the internal combustion engine. If RPM exceeds the cold start RPM limit, then in accordance with steps  418  and  420  the “Engine Started Flag” is set to “True”, the starter disabled, “ACC” functions enabled and the “Start Engine Request” flag set to “False”. Otherwise, if RPM is less than or equal to the cold start RPM limit, then a comparison of the elapsed engine crank time and the crank time limit is performed in accordance with step  422  described above. 
     Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention. It is intended that the invention be limited only by the appended claims.
A method for starting a motor vehicle having an internal combustion engine, an operator actuatable switch, an electric starter and a corresponding starter relay includes coupling a first control circuit to the starter relay during one or more crank operations, and coupling a second control circuit to the starter relay during the one or more crank operations, the coupling steps resulting in a minimal delay time associated with the starting of the motor vehicle.