Possible Causes
• Diagnostic Codes
• Fuel Level Misreading
• Fuel Leakage
• Fuel Quality
• Engine Oil Quality
• Coolant Temperature
• Prolonged Idling
• Intake and Exhaust Systems
• Cooling Fan
• Reduced Intake Pressure
• Excessive Valve Clearance
• Faulty Main Speed/Timing Sensor
Recommended Actions
Note: These steps are listed below in order of probability. Perform these steps in sequence.
Troubleshooting and Troubleshooting Test Step Results
1. Diagnostic Codes Note: Some diagnostic codes and/or event codes may cause excessive fuel consumption. A. Before performing any troubleshooting and troubleshooting or clearing any diagnostic codes, download the warranty report and bar chart product status report. Note: If troubleshooting and troubleshooting assistance is required, the Dealer Solutions Network (DSN) will request the download of information.
B. Use electronic service tools to check active or recorded codes. Diagnostic Code Result: Diagnostic code present.
Repair: Diagnose and troubleshoot the code, then confirm normal fuel consumption.
Result: Diagnostic code not present.
Proceed to test step 2. 2. Misreading Fuel Level Note: Misreading the fuel gauge will incorrectly indicate fuel consumption. A. Monitor fuel consumption over 50 engine operating hours. Fuel Level Result: Fuel consumption is normal relative to operating conditions. Return the unit to operation. Result: Fuel consumption is higher than normal relative to operating conditions. Proceed to test step 3.
3. Fuel Leak A. Check the engine for signs of fuel leaks. Fuel Leak Result: Signs of fuel leak found. Repair: Repair or replace the leaking component. Result: No signs of fuel leak found. Proceed to test step 4.
4. Fuel Quality Note: Fuel grade affects fuel consumption rate. Refer to the Engine Operation and Maintenance Manual for more information. Cold weather can adversely affect fuel characteristics. Refer to the Operation and Maintenance Manual for information on improving fuel characteristics during cold weather operation. A. Check fuel quality. Refer to System Operation, Testing and Adjustment, “Fuel Quality – Testing”. Fuel Quality Result: Fuel quality does not meet technical specifications. Repair: Drain the fuel system and replace the fuel filter. Refer to the Operation and Maintenance Manual, “Fuel System Coarse Filter (Fuel-Water Separator) Filter Element – Replacement” and the Operation and Maintenance Manual, “Fuel System Filter – Replacement”. Add fuel to the fuel system according to the standards in the Operation and Maintenance Manual, “Fuel Fluid Recommendations”. Fuel system filling. Refer to the Operation and Maintenance Manual, “Fuel System – Filling”. B. Refer to the Operation and Maintenance Manual for information on the appropriate fuel characteristics for the engine. Result: Fuel quality meets technical specifications. Proceed to test step 5.
5. Engine Oil Quality Note: The nominal viscosity of the engine oil affects fuel consumption. Engine oil viscosity is defined by the SAE grade. The grade of the engine oil must be suitable for environmental conditions. High ambient temperatures can affect fuel consumption at low ambient temperatures. A. Check and confirm that the engine oil meets the required technical specifications. Refer to the Operation and Maintenance Manual, “Addition Capacity,” under “Engine Oil.” Engine Oil Quality Result: The engine oil does not meet the required technical specifications. Repair: Drain the oil system and add oil of acceptable quality. Refer to the relevant section in the Operation and Maintenance Manual. Result: The engine oil meets the required technical specifications. Proceed to test step 6.
6. Coolant Temperature Note: Engine operating temperature affects fuel consumption. Operating the engine below the appropriate temperature increases fuel consumption. A faulty coolant temperature regulator may prevent the engine from operating at the correct temperature. A. Check if the coolant temperature regulator is working properly. Please refer to System Operation, Testing and Adjustment, “Coolant Temperature Regulator – Test”. Coolant Temperature Result: The coolant temperature regulator is not working properly. Repair: Replace the coolant temperature regulator. The fault was confirmed to be resolved after the repair. Result: The coolant temperature regulator is working properly. Proceed to test step 7.
7. Prolonged Idling Note: Prolonged engine idling increases fuel consumption. A. Check if the engine has been idling for a long time. Prolonged Idling Result: The engine has been idling for a long time. If possible, turn off the engine to save fuel. Result: The engine has not been idling for a long time. Proceed to test step 8.
8. Intake and Exhaust System A. Check the air filter blockage indicator (if present). B. Check the intake and exhaust systems for the following faults: · Blockage · Obstruction · Damaged pipes or hoses Intake and Exhaust System Blockage Result: Air filter blocked. Repair: Replace the air filter. Result: System blockage. Repair: For more information on the intake and exhaust systems, refer to System Operation/Testing and Adjustment, “Intake and Exhaust Systems”. Result: Intake and exhaust systems are normal. Proceed to test step
9. 9. Cooling Fan Note: Overuse or damage to the cooling fan will increase fuel consumption. A. Check the operation and condition of the cooling fan. Cooling Fan Result: Cooling fan overuse. Repair: Repair or replace the faulty cooling fan component. Result: Cooling fan overuse. Repair: Repair or replace the faulty cooling fan component. Result: Cooling fan not overuse and not damaged. Proceed to test step 10.
11. Excessive Valve Clearance A. Check if the valve clearance is excessive. Valve Clearance Result: Incorrect valve clearance. Repair: Check the valve clearance. For correct procedures, see System Operation, Testing and Adjustment, “Engine Valve Clearance – Check”. Result: Correct valve clearance. Proceed to test step 12.
12. Main Speed/Timing Sensor Fault Main Speed/Timing Sensor Malfunction Result: The main speed/timing sensor is malfunctioning. A. Rotate the engine and observe the engine speed on the electronic repair tool status screen. Initially, the engine speed status will indicate an abnormal engine speed signal. Once the ECM can calculate the speed from the signal, this information will be replaced by the engine speed. Repair: Test the main speed/timing sensor. Please refer to Troubleshooting and Troubleshooting, “Speed/Timing – Test”. Result: The main speed/timing sensor is functioning correctly. Please contact the Distributor Solutions Network (DSN).
