Yale 655-5 – Engine Control Unit (ECU): GM Gas Drive Injector 5 Open Circuit

The engine controller is detecting a lack of electrical current on the drive circuit for fuel injector #5 when voltage is applied. The system is trying to pulse the injector to deliver fuel, but the electrical loop is broken.

• Yale and Hyster Forklifts
• Yale VX Series (GC/GLC/GP/GLP 040-070VX, GC135VX)
• Hyster FT Series

1. 1

   Disconnect the battery, discharge system capacitors, and visually inspect the Injector #5 electrical connector and wiring for breaks, corrosion, or loose pins.

2. 2

   Perform an Ohm/resistance test on Injector #5 by disconnecting the plug and measuring across the two pins with a multimeter. A reading of 'OL' or infinite resistance indicates a dead injector coil.

3. 3

   Check the continuity of the wiring harness from the injector connector back to the ECU pins to rule out a broken wire.

4. 4

   Perform a swap test by exchanging Injector #5 with Injector #4. Clear codes and crank the engine; if the code changes to 654-5, the injector is faulty. If 655-5 remains, the issue is in the wiring harness or ECU.

1. 1

   Prep the Machine

   Park the forklift on a level surface, lower the forks, apply the parking brake, and turn off the ignition. Disconnect the battery.

2. 2

   Relieve Fuel Pressure

   For LPG trucks, close the valve on the LP tank and run the engine until it stalls to empty the lines. For gasoline trucks, relieve the pressure at the fuel rail Schrader valve.

3. 3

   Access the Injector

   Remove the engine cover to access the GM 4.3L intake manifold.

4. 4

   Remove the Injector

   Disconnect the electrical plug from Injector #5. Depending on the specific fuel system (e.g., GFI or IMPCO), remove the retaining clips or unbolt the fuel rail/injector pod to free the injector.

5. 5

   Install the New Injector

   Lubricate the O-rings on the new injector with a small amount of clean oil to prevent tearing. Seat the injector firmly into the manifold/rail and reinstall the retaining clips.

6. 6

   Reassembly

   Reconnect the electrical plug. Re-pressurize the fuel system (open the LP tank valve or prime the gas pump) and check carefully for leaks.

7. 7

   Clear Codes

   Reconnect the battery. Turn the key to the ON position and use the dash display to clear the fault code history. Start the engine and verify the code does not return.