LOCKNUT 3F1960 - Caterpillar

Illustration 1 describes the diagnostic codes that relate to excessive soot.
Illustration 1 g01449927
Diagnostic trouble codes for excessive soot loadThese codes do not indicate that the Diesel Particulate Filter (DPF) must be replaced. Engine operation must be kept to a minimum in order to minimize the amount of soot that is created. Follow the troubleshooting procedure in order to minimize the amount of engine operation.The Engine Control Module (ECM) maintains an estimate of the soot load in the DPF. The estimate is based on the engine's operating conditions. If the ECM estimates that the soot load is excessive, the ECM activates the applicable code.
Table 1
Diagnostic Trouble Codes for Excessive Soot Load    
J1939 Code    Description    Information that Relates to the Code    
3719-16     Diesel Particulate Filter #1 Soot Load Percent : High - Moderate Severity (2)     The estimated soot load is high. The ECM shuts down the engine when this code becomes active for the first time. The engine can be started and operated. Engine power is gradually derated as the soot load increases.    
3719-0     Diesel Particulate Filter #1 Soot Load Percent : High - Most Severe (3)     The estimated soot load is very high. Engine operation is limited to 60 second intervals when the Caterpillar Electronic Technician (ET) is not communicating with the ECM.    
3715-31     Diesel Particulate Filter Active Regeneration Inhibited Due to Permanent System Lockout     The estimated soot load is very high. The engine may not operate properly. Factory passwords are required in order to clear this code.    
Follow the troubleshooting procedure in order to determine the root cause of the problem.    Troubleshooting Procedure
Perform this test step if you are troubleshooting a 3715-31 code. Otherwise, proceed to Test Step 2.Use the Caterpillar Electronic Technician (ET) to view the differential pressure across the DPF. If there are two filters, view the differential pressure across both of the filters. The differential pressure is indicated by the following parameters:
"Diesel Particulate Trap #1 Differential Pressure"
"Diesel Particulate Trap #2 Differential Pressure"You may need to create a new group in order to view these parameters.Start the engine. Increase the engine speed to 1400 rpm. Monitor the differential pressure for 30 seconds. Stop the engine.If the differential pressure exceeds 15.0 kPa (2.1 psi), replace the appropriate DPF. Use factory passwords in order to clear the 3715-31 code. Return the vehicle to service.If the differential pressure is less than 15.0 kPa (2.1 psi), do not replace the DPF. Use factory passwords in order to clear the 3715-31 code. Continue to the next test step.
If the vehicle is equipped with an ARD disable switch, verify that the switch is not disabling the Aftertreatment Regeneration Device (ARD). Refer to the vehicle's service manual in order to determine the proper operation of the switch.
Troubleshoot any diagnostic codes that relate to the following systems or conditions:
Fouled nozzle
Low boost
ARD
Clean Gas Induction System (CGI)Troubleshoot the systems in the order that is listed above if there are diagnostic codes for more