Method and device for diagnosing a reading

Abstract

A method for diagnosing a reading ( 10, 12 ) or the sensor ( 106, 110 ) delivering the reading, whereby the sensor ( 106, 110 ) is spatially and/or functionally associated with an exhaust gas catalytic converter unit ( 108 ) which is arranged after a combustion engine ( 100 ) and a device functioning according to the method are provided, whereby a first reading ( 10 ) from a first sensor ( 106 ), arranged before the exhaust gas catalytic converter unit ( 108 ) in the flow direction of the exhaust gas and a second reading ( 12 ) from a second sensor ( 110 ), arranged after the exhaust gas catalytic converter unit ( 108 ) in the flow direction of the exhaust gas, is processed, whereby a special operating state of the combustion engine ( 100 ) is awaited or induced and, upon reaching the special operating state, it is monitored whether the first and second reading ( 10, 12 ) fall below a first threshold value ( 16 ) within a predetermined or predeterminable first time span ( 18 ).

1 . In a system comprising a combustion engine producing an exhaust gas, a catalytic converter for processing said exhaust gas, a first sensor arranged in the exhaust gas upstream of the catalytic converter and providing a first reading, and a second sensor arranged in the exhaust gas downstream of the catalytic converter and producing a second reading, a method for diagnosing at least one of the first or second readings or at least one of the first or second sensors, said method comprising 
 inducing a special operating state of the combustion engine; and    upon reaching the special operating state, monitoring the first reading and the second reading to determine if either the first reading or the second reading is less than a first threshold value within a first time span following said special operating state.    
   
   
       2 . The method according to  claim 1 , 
 wherein no fuel is supplied to the combustion engine in the special operating state.    
   
   
       3 . The method according to  claim 1 , further comprising 
 if both the first reading and the second reading is less than the first threshold value within the first time span, determining whether both the first reading and the second reading remains less than the first threshold value during a second time span.    
   
   
       4 . The method according to  claim 3 , further comprising 
 incrementing or decrementing a counter if one of the first reading or the second reading exceeds the first threshold value within the second time span.    
   
   
       5 . The method according to  claim 4 , further comprising 
 determining a counter threshold value for the status of the counter, and generating a signal if the counter is equal to the counter threshold value.    
   
   
       6 . The method according to  claim 1 , further comprising 
 determining a steady state deviation between the first reading and the second reading, and adding the steady state deviation to one of the first reading and the second reading during the second time span.    
   
   
       7 . The method according to  claim 1 , further comprising 
 diagnosing the catalytic converter unit based upon a diagnosis of the first reading and the second reading or at least one of the first or second sensors during the special operating state.    
   
   
       8 . A diagnosis device for use in a system comprising a combustion engine producing an exhaust gas, a catalytic converter for processing said exhaust gas, a first sensor arranged in the exhaust gas upstream of the catalytic converter and providing a first reading, and a second sensor arranged in the exhaust gas downstream of the catalytic converter and producing a second reading, said diagnosing device for diagnosing at least one of the first or second readings or at least one of the first or second sensors, comprising 
 means for inducing a special operating state of the combustion engine; and    means for monitoring the first reading and the second reading upon reaching the special operating state to determine if either the first reading or the second reading is less than a first threshold value within a first time span following said special operating state.    
   
   
       9 . The diagnosis device according to  claim 8 , comprising 
 at least one processing unit having an input for receiving the first reading and the second reading, whereby the processing unit executes a program code.    
   
   
       10 . A computer program data transferable into a memory of a processing unit for operating a diagnosis device for use in a system comprising a combustion engine producing an exhaust gas, a catalytic converter for processing said exhaust gas, a first sensor arranged in the exhaust gas upstream of the catalytic converter and providing a first reading, and a second sensor arranged in the exhaust gas downstream of the catalytic converter and producing a second reading, said computer program comprising instructions performable by said processing unit for diagnosing at least one of the first or second readings or at least one of the first or second sensor, said computer program comprising 
 instructions including instructions for inducing a special operating state of the combustion engine; and    instructions for monitoring the first reading and the second reading upon reaching the special operating state to determine if either the first reading or the second reading is less than a first threshold value within a first time span following said special operating state.