Diagnostic circuit for vehicle device control module

Abstract

A control module for a vehicle device control system contains a diagnostic circuit with one or more ASICs having a plurality of loops. The loops may contain either a squib, forming a squib loop, or a replacement resistor, forming a replacement resistor loop. A multiplexer connected to one loop of the ASIC diagnoses all of the replacement resistor loops. By using a multiplexer to detect replacement resistors, the invention eliminates the need to include an additional ASIC just to diagnose the replacement resistor loops.

What is claimed is:  
     
       1. A control module for a vehicle having at least one device containing a squib and at least one device containing a replacement resistor, the control module comprising: 
       a circuit having a plurality of loops, wherein at least one loop is a squib loop containing the squib; and  
       a multiplexer connected to at least one of said plurality of loops, wherein the multiplexer forms at least one replacement resistor loop containing the replacement resistor.  
     
     
       2. The control module of  claim 1 , wherein the vehicle contains a plurality of squibs and a plurality of replacement resistors, and wherein the ASIC has a plurality of squib loops, each squib loop containing one of said plurality of squibs. 
     
     
       3. The control module of  claim 2 , wherein the multiplexer forms a plurality of replacement resistor loops, each replacement resistor loop containing one of said plurality of replacement resistors. 
     
     
       4. The control module of  claim 1 , further comprising a microcontroller that controls at least one of the circuit and the multiplexer. 
     
     
       5. A control module for a vehicle having a first plurality of devices each containing a squib and a second plurality of devices each containing a replacement resistor, the control module comprising: 
       an application specific integrated circuit (ASIC) having a plurality of loops, wherein at least one loop is a squib loop containing the squib in one of said first plurality of devices;  
       a multiplexer connected to at least one of said plurality of loops, wherein the multiplexer forms a plurality of replacement resistor loops that each containing the replacement resistor in one of said second plurality of devices; and a microcontroller that controls operation at least one of the ASIC and the multiplexer.  
     
     
       6. The control module of  claim 5 , wherein the microcontroller controls operation of both the ASIC and the multiplexer. 
     
     
       7. A method of diagnosing a first plurality of vehicle devices each containing a squib and a second plurality of vehicle devices each containing a replacement resistor, the method of comprising: 
       connecting each squib in said first plurality of vehicle devices to a circuit to form a plurality of squib loops;  
       connecting at least one of the loops in the circuit to a multiplexer; and  
       connecting each replacement resistor to the multiplexer to form a plurality of replacement resistor loops; and  
       monitoring the plurality of squib loops and the plurality of replacement resistor loops.