SHOE-TRACK 7T2750 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the following diagnostic codes:
3002-2 Engine Exhaust NOx Level Sensor erratic, intermittent, or incorrect
3002-4 Engine Exhaust NOx Level Sensor voltage below normal
3002-6 Engine Exhaust NOx Level Sensor current above normal
3002-9 Engine Exhaust NOx Level Sensor abnormal update rate
3002-12 Engine Exhaust NOx Level Sensor failureAlso, use this procedure to troubleshoot the following event codes:
E717 Engine Exhaust NOx Level Sensor Operating Temperature Not Reached
E727 Engine Exhaust Emissions Feedback Feature Manually DisabledThe NOX sensor is used by the Electronic Control Module (ECM) to measure the NOX concentration of 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 for optimum performance at reduced exhaust emissions.The NOX sensor 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 sensor heating element reaches this temperature, the sensor begins sending valid NOX data to the sensor buffer.Sensor buffer - The sensor buffer is used to process the measurements that are received from the sensor. The buffer transmits these measurements 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 Pulse Width Modulated output (PWM) at the ECM. The sensor buffer requires 18 to 36 V in order to operate.The sensor is powered up by the buffer after the following conditions are verified:
No active diagnostic codes that are related to the NOX sensor
Engine speed above 500 rpmThe sensor and the sensor buffer are integrated parts. The sensor and the sensor buffer must be replaced as a single component, if necessary. The following codes are used by the ECM in order to communicate diagnostic information to the technician:3002-2 - The NOX sensor informs the ECM that the data from the sensor is incorrect.3002-4 - The NOX sensor informs the ECM that the sensor supply voltage is out of specifications.3002-6 - The ECM has detected a short circuit in the voltage supply that is for the NOX sensor.3002-9 - The ECM cannot communicate with the NOX sensor. There may be a problem in the circuit that is for the CAN data link.3002-12 - The NOX sensor reports an internal fault to the ECM.E717 - The ECM determined that the NOX sensor has not reached operating temperature within a specified amount of time.E727 - The E727 event code is generated when the "Emissions Feedback Mode configuration" parameter is set to "Feedback Disabled". This feature allows the feedback mode to be disabled in order to troubleshoot the engine. For example, disabling of this feature can help determine if the air/fuel ratio control is the cause