COUPLING GP 3843700 - Caterpillar

Probable Causes
NOx Reduction System (NRS) cooler
Cylinder head gasket
Cylinder head
Cylinder blockRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.Note: After the repair has been made, the electronic service tool must be used to perform an "Aftertreatment System Functional Test". The test will verify the correct functionality of both NOx sensors and the catalysts.
Table 1
Troubleshooting Test Steps Values Results
1. NRS cooler
A. Check the NRS cooler for leaks for utilizing the "On Engine Test Procedure". Refer to Systems Operation, Testing, and Adjusting, "Exhaust Cooler (NRS) - Test".
NRS cooler
Result : The NRS cooler has a leak.
Repair: Replace the NRS cooler. Refer to the Disassembly and Assembly manual for the correct procedure.
Proceed to Step 5.
Result : The NRS cooler does not have a leak.
Proceed to Test Step 2.
2. Cylinder head gasket leak
A. Check the cylinder head gasket for leaks.
Cylinder head gasket
Result : The cylinder head gasket is leaking.
Proceed to Test Step 3.
Result : The cylinder head gasket is not leaking.
Proceed to Test Step 3.
3. Cylinder head
A. Check for cracks in the cylinder head. Perform a leak test on the cylinder head. Refer to the Systems Operation, Testing, and Adjusting, "Cylinder Head - Inspect" for the correct procedure.
Cylinder head
Result : A crack is found in the cylinder head.
Repair: Repair the cylinder head or replace the cylinder head. Refer to the Disassembly and Assembly manual.
Proceed to Test Step 4.
Result : The cylinder head is OK.
Proceed to Test Step 4.
4. Cylinder Block
A. Check for cracks in top face of the cylinder block. Refer to the Systems Operation, Testing, and Adjusting, "Cylinder Block - Inspect" for the correct procedure.
Cylinder head
Result : A crack is found in the cylinder block.
Repair: Repair the cylinder block or replace the cylinder block. Refer to the Disassembly and Assembly manual.
Repair: Assemble the cylinder head with a new cylinder head gasket. Refer to the Disassembly and Assembly manual.
Proceed to Test Step 5.
Result : The cylinder block is OK.
Repair: Assemble the cylinder head with a new cylinder head gasket. Refer to the Disassembly and Assembly manual.
Proceed to Test Step 5.
5. Perform an "Aftertreatment System Functional Test"
A. Start the engine.
B. Connect the electronic service tool to the diagnostic connector.
C. Navigate to "Diagnostics Tests".
D. Perform the "Aftertreatment System Functional Test".
System test
Result : The test is successful.
Return the engine to service.
Result : The test is not successful.
There are additional diagnostic codes.
Repair: Troubleshoot the additional codes. Refer to Troubleshooting, "Diagnostic Trouble Codes" manual for the correct procedure.