19221-ZY3-000 Honda HOUSING, IMPELLER (Honda Code 6990790).

Probable Causes
Diagnostic codes
ECM Flash file
Glow plugs
Coolant temperature
Cooling system
Fuel quality
Valve lash
Low compression (cylinder pressure)
Electronic unit injectors
Individual malfunctioning cylinderRecommended Actions
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
A. Establish communication between the electronic service tool and the Electronic Control Module (ECM) . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Download the Warranty Report and the Product Status Report with Histograms before performing any troubleshooting or clearing any diagnostic codes.
Note: The downloaded information will be required by the Dealer Solutions Network (DSN) if troubleshooting assistance is needed.
C. Determine if a code is active or logged.
Diagnostic codes
Result: A code is active or logged.
Repair: Troubleshoot any active codes before continuing with this procedure.
Result: A code is not active or logged.
Proceed to Test Step 2.
2. ECM Flash File
A. Verify that the latest flash file is installed in the ECM.
Flash file
Result: The latest flash file is not installed.
Repair: Install the latest flash file. Refer to Troubleshooting, "ECM Software - Install" for the correct procedure. Verify that the repair eliminates the fault.
Result: The latest flash file is installed.
Proceed to Test Step 3.
3. Glow Plugs
Note: Faulty glow plugs will only affect the production of white smoke when the ambient temperature is between 5° C (41° F) and −25° C (−13° F).
A. Check operation of glow plugs. Verify that the glow plugs are operating correctly. Refer to Troubleshooting, "Glow Plug Starting Aid - Test".
B. Check the configuration screen on the electronic service tool to verify that ether injection is not enabled.
Glow plugs
Result: The glow plugs are not operating correctly.
Repair: Make the necessary repairs. Verify that the repair corrected the fault.
Result: The glow plugs are operating correctly.
Proceed to Test Step 4.
4. Coolant Temperature
A. Check that the water temperature regulator is operating correctly. Refer to Systems Operation, Testing, and Adjusting, "Water Temperature Regulator - Test".
Coolant temperature
Result: The water temperature regulator is not operating correctly.
Repair: Replace the water temperature regulator. Verify that the repair corrected the fault.
Result: The water temperature regulator is operating correctly.
Proceed to Test Step 5.
5. 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 fault.
Result: There is not an internal coolant leak.
Proceed to Test Step 6.
6. 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 proper 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 the 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".
Result: The fuel quality is OK.
Proceed to Test Step 7.
7. Valve Lash
Note: The valve lash can affect the performance of the engine.
A. Check the valve lash.
Valve lash
Result: The valve lash is not set correctly.
Repair: Check the valve lash. Refer to Systems Operation, Testing, and Adjusting, "Engine Valve Lash - Inspect" for the correct procedure.
Result: The valve lash is correct.
Proceed to Test Step 8.
8. 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
Result: The results of the compression test are OK.
Proceed to Test Step 9.
9. Electronic Unit Injectors
A. Use the electronic service tool to perform the automatic "Cylinder Cut Out Test".
Note: If the compression test that was performed in Test Step 9 was satisfactory, the "Cylinder Cut Out 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 Cut Out 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 10.
10. Individual Malfunctioning Cylinders
A. With the engine speed at a fast idle, use the electronic service tool to perform the manual "Cylinder Cut Out Test".
As each cylinder is cut out, listen for a change in the sound from the engine. When a cylinder is cut out, there should be a noticeable change in the sound of the engine.
Note: If a change in the sound of the engine is not noted, the isolated cylinder is not operating under normal conditions. If the isolation of a cylinder results in a change in the sound that is less noticeable, the cylinder may be operating below normal performance.
Cylinders
Result: The test indicates a faulty cylinder.
Repair: Investigate the cause of the fault on any cylinder that is not operating. Investigate the cause of the fault on any cylinder that is operating below normal performance.
Result: The test indicates that all cylinders are OK.
Contact the Dealer Solutions Network (DSN).