24625-ZV5-010 Honda SEE PART DETAILS - PRI; PLATE, SHIFT (Honda Code 7493950).

Table 1
J1939 Code and Description CDL Code and Description Comments
6646-18
Engine Gas Supply Pressure : Low - moderate severity (2) E221 (2)
Low Gas Supply Pressure Gas supply pressure from Liquid Natural Gas (LNG) tank is below operating requirements of 350 kPag (50 psig) and tank level greater than 25 percent.
The code is logged.
7021-14
Engine Fuel #2 Injector Metering Rail #1 Pressure : Special Instruction 4755-14
Engine Fuel #2 Injector Metering Rail Pressure Sensor #1 : Special Instruction The Electronic Control Module (ECM) has detected a pressure drop in the gaseous fuel supply which exceeds allowable leak down rates.
Gas blending will be "Disabled". Probable Causes
Codes
Gas level
Filter
Sensor
Gas system
Relief valves
Excess flow valveRecommended Actions
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Look for active codes that are associated with the system for the event code.
Codes
Result: An associated code is active.
Repair: Troubleshoot any associated codes before continuing with this test.
Result: A code is active or logged.
Proceed to Test Step 2.
2. Inspect the Liquid Natural Gas (LNG) Tank
A. Check the LNG tank level.
B. Verify that the LNG tank isolation valve is OPEN.
Note: If tank pressure is less than 350 kPag (50 psig) and the level shows full, then the LNG tank needs to be defueled and refilled with LNG that is conditioned to acceptable pressure.
Level and Pressure
Result: The LNG tank level and pressure is acceptable.
Proceed to Test Step 3.
Result: The LNG tank is not filled properly.
Repair: Defuel the LNG tank and refilled with LNG that is conditioned to acceptable pressure.
Fuel may not be conditioned to the correct temperature range at the fuel station. Ensure that the fuel stored in the dispensing tank at the station is within the temperature range of −135° C to −125° C (−211° F to −193° F), or approximately 517 kPag to 896 kPag (75 psig to 130 psig).
If the problem is not resolved, proceed to Test Step 3.
3. Check for a Plugged Gas Filter
Filter
Result: The gas filter is not plugged.
Proceed to Test Step 4.
Result: The gas filter is plugged.
Repair: Change the gas filter.
If the problem is not resolved, proceed to Test Step 4.
4. Inspect the LNG Tank Level Sensor
A. Check for a faulty sensor box.
B. Check for a broken coax wire.
C. Check for a faulty or loose signal wire and/or sensor box connections.
E. Check the accuracy of the level sensor at empty tank condition. Refer to Operations and Maintenance Manual, Fuel Tank-Drain to verify that the LNG tank is empty.
F. Verify that the LNG tank level sensor capacitance is within specifications.
a. Remove the cable from the sensor box to the tank.
b. Check the tank sensor capacitance using the Cat specified LCR meter.
c. Connect the meter cable directly to the tank cable output.
Note: The capacitance excluding the cable used to connect to the tank should read between 700 +/- 50 pF with the tank empty.
Sensor
Result: The level sensor is reading correctly.
Proceed to Test Step 5.
Result: There is a broken or loose wire and/or faulty sensor box.
Repair: Repair or replace the damaged components.
If the problem is not resolved, proceed to Test Step 5.
Result: The LNG tank is empty and the level sensor is reading greater than 25%.
Repair: Perform the "Engine Fuel #2 Tank Level Empty Calibration" procedure within Cat ET Service Calibrations.
If the problem is not resolved, proceed to Test Step 5.
Result: The LNG tank level sensor capacitance is not within specifications.
Repair: Replace the sensor box.
If the problem is not resolved, proceed to Test Step 5.
5. Inspect the Gas System
A. Check all fittings and seals for leaks with a methane detector or soapy water.
Gas System
Result: The gas system is OK.
Proceed to Test Step 6.
Result: An external leak was found.
Repair: Perform the following procedure:
1. Shutoff the Liquid Natural Gas (LNG) tank valve and/or isolate the leak from LNG tank pressure.
2. Repair or replace the damaged gas system components.
3. Check the repair with a methane detector or soapy water.
If the problem is not resolved, proceed to Test Step 6.
6. Inspect the Pressure Relief Valves and Vent Lines
A. Check the relief valves for wear or damage.
B. Check the vent lines for signs of frost, and inspect the outlet of the vent stack for indications of gas flow.
Relief Valves
Result: The relief valves and vent lines are OK.
Proceed to Test Step 7.
Result: The relief valves are NOT OK. Frost is present on the vent lines or gas is flowing out the vent stack, and LNG tank pressure is less than the pressure relief set point of the pressure relief valve.
Repair: A relief valve is leaking. Replace the relief valve.
If the problem is not resolved, proceed to Test Step 7.
7. Inspect the Excess Flow Valve (EFV) functionality for the LNG Tank
A. Actuate the EFV by quickly opening the manual chassis manual vent valve with LNG in the tank at pressure greater than 689 kPa (100 psi).
B. Verify that the EFV closed and stopped the flow of gas through the vent stack by inspecting the vent stack. In addition, if background noise is minimal, basic valve operation can be confirmed by an audible sound.
C. Verify the EFV resets position and opens properly by closing the manual chassis vent valve. Gas pressure to the engine will slowly recover and after a few minutes the EFV will reset open. If background noise is minimal, basic valve operation can be confirmed by an audible sound.
Excess Flow Valve
Result: The EFV is OK.
Return to service.
Result: The EFV is NOT OK.
Repair: Replace the EFV.
Verify that the repair eliminated the problem.
If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).