BUSHING 9W4195 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the NOX sensor group. Also, use this procedure if one of the diagnostic codes or the event code in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table    
Description    Conditions which Generate this Code    System Response    
3002-2 Engine Exhaust NOx Level Sensor : Erratic, Intermittent, or Incorrect     The Electronic Control Module (ECM) has received a communication that indicates that the data from the NOX sensor is incorrect.     The power to the sensor is turned off.
NOX feedback is turned off.
The fuel correction factor is locked at the last value that is known to be good.
The code is logged.
The alarm output is activated.    
3002-9 Engine Exhaust NOx Level Sensor : Abnormal Update Rate     The ECM has not received several messages that were expected from the NOX sensor over the CAN data link.     NOX feedback is turned off.
The fuel correction factor is locked at the last value that is known to be good.
The code is logged.
The alarm output is activated.    
3002-12 Engine Exhaust NOx Level Sensor : Failure     The ECM has received communications from the NOX sensor that indicates that an internal fault has been detected.     NOX feedback is turned off.
The fuel correction factor is locked at the last value that is known to be good.
The code is logged.
The alarm output is activated.
The shutdown output is activated.
The engine is shut down.    
E717(1) Engine Exhaust NOx Level Sensor Operating Temperature Not Reached     The ECM has not received a communication that is expected from the NOX sensor. The communication reports that the operating temperature of the sensor has been reached.     NOX feedback is turned off.
The fuel correction factor is locked at the last value that is known to be good.
The code is logged.
The alarm output is activated.    The NOX sensor group is used by the ECM to measure the level of NOX concentration in the engine exhaust. This value is reported back to the ECM via the CAN data Link. The ECM uses this information to control the air/fuel ratio for the engine. By controlling the air/fuel ratio, the ECM is able to control the engine operation for optimum performance at reduced exhaust emissions.The NOX sensor group is made up of two separate components:Sensor - The NOX sensor consists of a ceramic element that measures the concentration of NOX in the exhaust gas. The sensor contains a heating element that is used to heat the sensor to approximately 800 °C (1450 °F). Once the heating element reaches this temperature, the sensor begins sending NOX data to the sensor buffer.Sensor buffer - The sensor buffer is used to process the signals that are received from the sensor. The buffer transmits this information to the ECM via the CAN data link. The buffer also reports diagnostic data to the ECM over the CAN data link. The sensor buffer is powered through a