SENSOR AS-NOX 3721186 - Caterpillar

Probable Causes
Codes
Cold mode (if applicable).
Starting aids (if applicable)
Flash file
Cooling system
Fuel supply
Fuel injection
TurbochargerRecommended Actions
Table 1
Troubleshooting Test Steps Values Results
1. Check for Active Codes and Logged Codes
A. Establish communication between Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM) . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Monitor the diagnostic codes on Cat ET. Determine if a code is active or logged.
Note: Wait at least 30 seconds in order for diagnostic codes to become active.
Codes
Result: A code is active or logged.
Repair: Troubleshoot any codes before continuing with this procedure.
Verify that the repair eliminated the problem.
Result: A code is not active or logged.
Proceed to Test Step 2.
2. Check for Cold Mode Operation (if applicable)
During cold mode operation, condensation may be present and is normal.
A. Cold mode is activated whenever the engine coolant temperature falls below a predetermined value. Monitor the status screen on Cat ET to verify that the engine has exited cold mode. Observe the reading for coolant temperature on the Cat ET.
Cold Mode
Result: The engine is operating in cold mode.
Repair: This is normal operation. Return the engine to service.
Result: The engine is not operating in cold mode.
Proceed to Test Step 3.
3. Check the Starting Aids (If Applicable)
A. If cold ambient conditions exist, check operation of starting aids. Verify that the starting aid is operating correctly. Refer to the appropriate circuit test for information that is related to troubleshooting the starting aid.
If ether bottles are not installed, check the configuration screen on Cat ET to verify that ether is not enabled.
Starting Aid
Result: The starting aid is operating correctly.
Proceed to Test Step 4.
Result: The starting aid is not operating correctly.
Repair: Make the necessary repairs.
Verify that the repair eliminated the problem.
4. Ensure that the latest Flash File is Installed on the ECM
A. Verify that the latest flash file is installed in the ECM. Refer to Troubleshooting, "ECM Software - Install" for the proper procedure.
Flash file
Result: The latest flash file is installed.
Proceed to Test Step 5.
Result: The latest flash file is not installed.
Repair: Install the latest flash file.
Verify that the repair eliminated the problem.
5. Inspect the Cooling System
A. Check for an internal coolant leak into the cylinder and/or the exhaust. Refer to Systems Operation/Testing and Adjusting, "Cooling System".
Internal Coolant Leak
Result: There is an internal coolant leak.
Repair: Make the necessary repairs.
Verify that the repair eliminated the problem.
Result: There is not an internal coolant leak.
Proceed to Test Step 6.
6. Check for an Unstable Fuel Supply
A. Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only.
B. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
C. Inspect the fuel system. Refer to Systems Operation/Testing and Adjusting, "Fuel System - Inspect" for additional information.
Cold weather adversely affects the characteristics of the fuel. Refer to the engines Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
D. Check fuel quality. Check the fuel tank for debris or foreign objects which may block the fuel supply.
E. Check the filtered fuel