LINK AS 5158572 - Caterpillar

Table 1
Event Code
J1939 Code Description Comments
7504-16 Aftertreatment #1 SCR System Sulfation Level : High - moderate severity (2) Sulfation of the SCR catalyst has exceeded an acceptable level.
7504-0 Aftertreatment #1 SCR System Sulfation Level : High - most severe (3) Sulfation of the SCR catalyst has exceeded an acceptable level. Over time, sulfur from the diesel fuel builds up on the SCR catalyst. When sulfation becomes excessive the catalyst loses the ability to convert NOx, resulting in higher emissions.The sulfur deposited on the catalyst can be removed by operating the engine at high exhaust temperatures for an extended period.The engine must be operated so the SCR intake gas temperature exceeds one of the following:
400° C (752° F) for a minimum duration of 30 minutes.Note: The required temperature threshold must be exceeded for the minimum duration or the desulfation process will be voided.If the desulfation process is voided, the next time the temperature threshold is exceeded the duration timer will start from zero.When the temperature requirement is maintained for the minimum duration, the desulfation process is completed and the active code will be removed.
Table 2
Troubleshooting Test Steps Values Results
1. Elevate the Engine Exhaust Temperature by Applying the Normal Load
A. Start the engine and allow the engine to reach normal operating temperature.
B. Apply load to the engine by engaging the Header and the Thresher.
C. Monitor the "SCR Inlet Temperature" parameter.
Target Temperature
400° C (752° F)
Result: The target temperature was exceeded.
Proceed to Step 4.
Result: The target temperature was not exceeded.
Proceed to Step 2.
2. Elevate the Engine Exhaust Temperature by Cylinder Cutout
A. Start the engine and allow the engine to reach normal operating temperature.
B. Using Cat ET, gradually cut out cylinders.
C. Monitor the "SCR Inlet Temperature" parameter.
Note: Start with cylinders that are farthest from the turbocharger.
Do not cut out more than half of the total number of cylinders.
Target Temperature
400° C (752° F)
Result: The target temperature was exceeded.
Proceed to Step 4.
Result: The target temperature was not exceeded.
Proceed to Step 3.
3. Elevate the Engine Exhaust Temperature by Blocking the ATAAC
A. Gradually block off the ATAAC.
B. Monitor the "SCR Inlet Temperature" parameter.
Note: Watch for alarms. Monitor the "Air Intake Manifold Temperature" parameter and "Engine Coolant Temperature" parameter.
Do not exceed the parameters upper limit for the engine application.
Target Temperature
400° C (752° F)
Result: The target temperature was exceeded.
Proceed to Step 4.
4. Continue Operating the Engine Under the Current Conditions
A. Continue to exceed the target temperature for the minimum duration.
B. Monitor the "SCR Inlet Temperature" parameter.
Target Temperature and Duration
400° C (752° F)
Result: The code changed from an active status to a logged status after the minimum duration for the temperature.
The SCR catalyst is now OK.
Return the engine to service.