POST AS 4999745 - Caterpillar

Table 1
Diagnostic Trouble Codes    
J1939 Code    CDL Code    Code Description
(code descriptions may vary)    Comments    
3217-16     E1407 (2)     Aftertreatment #1 Intake O2 : High - moderate severity (2)     The Engine Out NOx Sensor is reading a higher than expected level of Oxygen (O2).    
3227-16     E1408 (2)     Aftertreatment #1 Outlet O2 : High - moderate severity (2)     The Tailpipe Out NOx Sensor is reading a higher than expected level of Oxygen (O2).    The exhaust system is equipped with two sensors that measure Oxides of Nitrogen (NOx) and Oxygen (O2). Sensor #1 is mounted in the exhaust pipe between the engine turbocharger and the Clean Emissions Module (CEM) and is referred to as the Engine Out NOx sensor. This sensor monitors the NOx and O2 coming out of the engine. Sensor #2 is mounted in the exhaust pipe after the Selective Catalyst Reduction (SCR) catalyst and is referred to as the Tailpipe Out NOx sensor. This sensor monitors the NOx and O2 exiting the SCR cannister. Follow the troubleshooting procedure in order to identify the root cause of the problem.
Table 2
Troubleshooting Test Steps    Values    Results    
1. Check if NOx Sensors are Installed Correctly
A. Locate the appropriate NOx Sensor.
B. Check if the sensor is installed properly.
   
Properly Installed / Not Installed Properly    
Result: The sensor is not installed properly.
Repair: Install the sensor properly. Refer to Special Instruction, REHS8151.
Proceed to Test Step 3.
Result: The sensor is installed properly.
Proceed to Test Step 2.
   
2. Check for Exhaust Leaks
A. Start the engine.
B. Check the exhaust system for proper installation.
C. Check for loose or broken exhaust joints.
D. Inspect the exhaust system between the turbocharger outlet and the tailpipe outlet for signs of an exhaust leak.
   
Exhaust Leaks
   
Result: An exhaust leak was found.
Repair: Repair or replace the component causing the exhaust leak.
Proceed to Test Step 3.
Result: An exhaust leak was not found.
Proceed to Test Step 3.
   
3. Perform an Aftertreatment NOx Sensor Functional Test
A. Turn the keyswitch to the ON position..
B. Connect to the "Engine #1 Aftertreatment Control ECM" using Cat ET.
C. Start the engine.
D. Perform an "Aftertreatment NOx Sensor Functional Test" using Cat® ET.
   
Test
   
Result: The "Aftertreatment NOx Sensor Functional Test" was successful.
Return the unit to service.
Result: The "Aftertreatment NOx Sensor Functional Test" was not successful.
Repair: Replace the failed sensor. Refer to Special Instruction, REHS8151.
Perform an "Aftertreatment NOx Sensor Functional Test" using Cat® ET to verify the repair.