19251-ZV1-010 Honda TUBE, WATER (S) (Honda Code 2650406).

Recommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
A. Establish communication between the electronic service tool and the Electronic Control Module (ECM).
B. Use the electronic service tool to check for active or logged codes.
Codes
Result: A diagnostic trouble code is active or logged.
Repair: Troubleshoot the active or logged codes.
Result: A diagnostic trouble code is not active or logged.
Proceed to Test Step 2.
2. Fuel Quality
A. Check the fuel quality. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test".
B. Refer to Operation and Maintenance Manual for information on the correct characteristics of the fuel for the engine.
Fuel
Result: The fuel quality is not OK.
Repair: Drain the fuel system and replace the fuel filters. Refer to Operation and Maintenance Manual, "Fuel System Primary Filter (Water Separator) Element - Replace" and Operation and Maintenance Manual, "Fuel System Filter - Replace".
Fill the fuel system with fuel that meets the standard in the Operation and Maintenance Manual, "Fluid Recommendations".
Prime the fuel system. Refer to the Operation and Maintenance Manual, "Fuel System - Prime".
Verify that the procedure has eliminated the noise.
Result: The fuel quality is OK.
Proceed to Test Step 3.
3. Valve Train Components
A. Check the valve lash. Refer to Troubleshooting, "Valve Lash Is Excessive".
B. Check for damage to valve train components. Remove the valve cover from the engine. Check the following items for damage:
Valve springs
Rocker shaft
Bridges
Pushrods
Camshaft followers
Refer to Disassembly and Assembly for additional information.
Valve train
Result: Valve train components are damaged.
Repair: Make the necessary repairs, Verify that the repair has eliminated the noise.
Result: The valve train components are not damaged.
Proceed to Test Step 4.
4. Low Compression (Cylinder Pressure)
A. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test".
Cylinder compression
Result: The results of the compression test are outside the specifications.
Repair: Investigate the cause and rectify any faults.
Note: Possible causes of low compression are shown in the following list:
Loose glow plugs
Faulty piston
Faulty piston rings
Worn cylinder bores
Worn valves
Faulty cylinder head gasket
Damaged cylinder head
Note: Any work completed to rectify any of the above faults where injectors are reused must include the use of CAT Fuel system cleaner (343-6210) upon engine recommission.
Result: The results of the compression test are OK.
Proceed to Test Step 5.
5. Electronic Unit Injectors
A. Use the electronic service tool to perform the automatic "Cylinder Cutout Test". Refer to Troubleshooting, Service Tool Features for more information on understanding the results of the "Cylinder Cutout Test".
Note: If the compression test that was performed in Test Step 4 was satisfactory, the "Cylinder Cutout Test" will identify any faulty injectors.
Electronic Unit Injectors
Result: A faulty injector is indicated.
Repair: Remove any faulty electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove".
Install new electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Install".
Repeat the automatic "Cylinder Cutout Test". If the fault is still apparent, remove the replacement electronic unit injector and install the original electronic unit injector. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove" and Disassembly and Assembly, "Electronic Unit Injector - Install".
Result: All injectors are OK.
Proceed to Test Step 6.
6. Pistons and Connecting Rods
A. Inspect the pistons for damage and wear.
B. Inspect the connecting rod bearings for damage and wear.
Pistons
Result: One or more components are worn or damaged.
Repair: Replace any worn or damaged parts.
Verify that the repair has eliminated the noise.
Result: All components are OK.
If the fault is still present, contact the Dealer Solutions Network (DSN).