12391-ZW5-000 Honda SEE PART DETAILS - SUP; GASKET, HEAD COVER (Honda Code 5890306).

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
Note: Certain diagnostic codes and/or event codes may cause high fuel consumption.
A. 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.
B. Use the electronic service tool to check for active or logged codes.
Diagnostic codes
Result: A diagnostic code is present.
Repair: Troubleshoot the code and then verify that the fuel consumption is normal.
Result: A diagnostic code is not present.
Proceed to Test Step 2.
2. Misreading of Fuel Level
Note: Misreading of the fuel gauge can give a false indication of fuel consumption.
A. Monitor the fuel consumption over a period of 50 engine hours.
Fuel level
Result: Fuel consumption is normal for the operating conditions.
Return the unit to service.
Result: Fuel consumption is high for the operating conditions.
Proceed to Test Step 3.
3. Fuel Leakage
A. Check the engine for signs of fuel leakage.
Fuel leaks
Result: Evidence of a fuel leak is found.
Repair: Repair or replace the component that is leaking fuel.
Result: No evidence of a fuel leak is found.
Proceed to Test Step 4.
4. Fuel Quality
Note: The grade of the fuel affects the rate of fuel consumption. Refer to the engines Operation and Maintenance Manual for additional information.
Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
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 quality
Result: The fuel quality does not meet specifications.
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 meets specifications.
Proceed to Test Step 5.
5. Quality of Oil
Note: The nominal viscosity of the lubricating oil that is used in the engine will affect the rate of fuel consumption. The viscosity of lubricating oil is defined by the SAE grade of the lubricating oil. The grade of the lubricating oil must be correct for the ambient conditions. Lubricating oil for high ambient temperatures will affect fuel consumption in cold ambient temperatures.
A. Check that the engine oil meets the required specification. Refer to "Engine Oil" in the Operation and Maintenance Manual, "Refill Capacities".
Engine oil quality
Result: The engine oil does not meet the required specification.
Repair: Drain and fill the oil system with oil of an acceptable quality. Refer to the applicable sections in the Operation and Maintenance Manual.
Result: The engine oil meets the required specification.
Proceed to Test Step 6.
6. Coolant Temperature
Note: The operating temperature of the engine will affect the rate of fuel consumption. Operation of the engine below the correct temperature will increase fuel consumption. Failure of the water temperature regulator can prevent the engine from operating at the correct 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 7.
7. Prolonged Operation at Idle Speed
Note: Prolonged operation of the engine at idle speed increases fuel consumption.
A. Check for extended periods of engine operation at idle speed.
Extended idle operation
Result: The engine is operating at idle speed for extended periods.
When possible, stop the engine to conserve fuel.
Result: The engine is not operating at idle speed for extended periods.
Proceed to Test Step 8.
8. Air Intake and Exhaust System
A. Check the air filter restriction indicator, if equipped.
B. Check the air intake and exhaust systems for the following defects:
Blockages
Restrictions
Damage to lines or hoses
Air and Exhaust System restrictions
Result: The air filter is restricted.
Repair: Replace the air filter.
Result: There are system restrictions.
Repair: Refer to Systems Operation/Testing and Adjusting, "Air Inlet and Exhaust System" for additional information on the air inlet and exhaust systems.
Result: The air intake and exhaust system is OK.
Proceed to Test Step 9.
9. Cooling Fan
Note: Excessive operation of the cooling fan or damage to the cooling fan will increase fuel consumption.
A. Check the operation and condition of the cooling fan.
Cooling fan
Result: The cooling fan is operating excessively.
Repair: Repair or replace the faulty cooling fan components.
Result: The cooling fan is damaged excessively.
Repair: Repair or replace the faulty cooling fan components.
Result: The cooling fan is not operating excessively and is not damaged.
Proceed to Test Step 10.
10. Reduced Pressure of Intake Air
Note: If the air pressure is lower than normal, the same power can only be achieved by the following:
Higher engine speed
Injection of more fuel
Either of these conditions will increase the fuel consumption.
A. Check all pipes from the outlets of the turbocharger compressor to the inlet manifold for leaks.
B. Check for the correct operation of the wastegate in the turbocharger.
Intake air
Result: There is a leak in the intake air system.
Repair: Repair the leak or replace the component that is causing the leak.
Result: The turbocharger wastegate is not operating correctly.
Repair: Replace the turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install".
If a turbocharger equipped with an electronic wastegate is replaced, use the electronic service tool to perform the "Turbocharger Wastegate Actuator Replacement Reset".
Use the electronic service tool to perform the "Air System Motor Valve Verification Test"
Result: The air intake system and the wastegate are OK.
Proceed to Test Step 11.
11. Excessive Valve Lash
A. Check for excessive valve lash.
Valve lash
Result: