17721-ZY3-000 Honda JOINT, FUEL RETURN (Honda Code 6990626).

The ECM limits the flow of fuel to prevent the engine speed from exceeding the value that is programmed into the ECM. When the engine speed has dropped to less than the value that is programmed into the ECM, the 190-x code will be reset.If the engine speed exceeds the value that is programmed into the ECM, the ECM illuminates the warning lamp and a 190-x code is logged. Factory passwords are required to clear the code. No troubleshooting is required.The history of engine overspeeds can be viewed on the electronic service tool.Probable Causes
Proceeding down steep grades (if applicable)
Diagnostic codes
Turbocharger
Combustible gases or liquid in the Intake airRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 2
Troubleshooting Test Steps Values Results
1. Proceeding Down Steep Grades (If Applicable)
Engaging the engine brakes on a steep grade may be necessary. Not all applications have engine brakes.
A. Make sure that the operator understands the correct operation of the machine while using the engine brakes.
Steep grades
Result: Steep grades are the cause of the overspeed.
Repair: Control the engine speed during steep grades.
Result: Steep grades are not the cause of the overspeed.
Proceed to Test Step 2.
2. Diagnostic Codes
A. Download 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 not active or logged.
Return the unit to service.
Result: At least one of the diagnostic codes listed in Table 1 is active or recently logged.
Proceed to Test Step 3.
3. Turbocharger
A. Check for any oil that may be leaking into the intake air.
Turbocharger
Result: The turbocharger is leaking oil into the intake air.
Repair: Repair the turbocharger or replace the turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install".
If the turbocharger 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"
Proceed to Test Step 5.
Result: A turbocharger is not leaking oil into the intake air.
Proceed to Test Step 4.
4. Combustible Gases or Liquid in the Intake Air
A. Check for combustible gases in the surrounding atmosphere.
B. Check for combustible liquid in the air intake.
C. Inspect the ether solenoid and cannister (if equipped), for leaks into the intake.
Air quality
Result: The atmosphere has combustible gases.
Repair: Do not operate the engine in an environment with combustible gases.
Result: There is combustible liquid in the air intake.
Repair: Remove the liquid. Investigate and rectify the cause of liquid ingestion
Result: The intake air does not contain combustible gases.
Contact the Dealer Solutions Network (DSN).
Result: The ether system is leaking.
Repair: Replace the ether system.
Result: The intake air does not contain combustible gases.
Contact the Dealer Solutions Network (DSN).
5. Check the Aftertreatment System for Oil
A. Remove excess oil from the piping with a clean cloth.
B. Remove the Clean Emissions Module (CEM). Refer to Disassembly and Assembly, "Clean Emissions Module - Remove and Install".
C. Support the CEM over a suitable container with the exhaust inlet downwards. Leave the CEM to drain for 8 hours.
D. Check the quantity of drained oil in the container.
CEM
Result The volume of drained oil is greater than 0.4 L (0.42 qt).
Repair: Install a replacement CEM. Refer to Disassembly and Assembly, "Clean Emissions Module - Remove and Install".
Return the unit to service.
Result The volume of drained oil is less than 0.4 L (0.42 qt).
Proceed to Test Step 6.
6. Recover the Aftertreatment System
A. Clean any remaining oil from the piping and the CEM inlet with a clean cloth.
B. Install the Clean Emissions Module (CEM). Refer to Disassembly and Assembly, "Clean Emissions Module - Remove and Install".
C. Run the engine at high idle with no load for a minimum of 20 minutes.
Note: During the following step, there are two versions of the "Aftertreatment Recovery Procedure". One version is for engines with a DPF. The other version is for engines without a DPF. Ensure that the correct procedure is used.
D. Use the electronic service tool to perform the "Aftertreatment Recovery Procedure". While the procedure is progressing, check for smoke from the exhaust. Some smoke will be evident during the procedure. The smoke must dissipate before the procedure is completed.
CEM
Result: The "Aftertreatment Recovery Procedure" completes with a soot load of less than 80% and no smoke from the exhaust.
Return the unit to service.
Result The "Aftertreatment Recovery Procedure" completes with a soot load of more than 80% or smoke from the exhaust.
Contact the Dealer Solutions Network (DSN).