Yale 522592-1 – Engine Control Unit (ECU): EPR Pressure Less Than Commanded

The Electronic Pressure Regulator (EPR) or Delivery Electronic Pressure Regulator (DEPR) is detecting a secondary fuel pressure that is lower than the target pressure commanded by the controller.

• Yale and Hyster Forklifts
• Yale (and Hyster) forklifts from 2005 and newer
• GLP VX-series
• GLC VX-series

1. 1

   Check for Fuel Restrictions: Inspect the vaporizer pressure and LPG gas filters. A clogged filter or a freezing vaporizer can restrict fuel flow. Drain the evaporator (hot).

2. 2

   Check the Power Supply: Locate and inspect the 10 Amp fuse that provides power to the EPR to ensure it is not blown.

3. 3

   Inspect Wiring and Connectors: Visually inspect the DEPR/EPR electrical connections for unseated pins, corrosion, opens, or shorts to ground.

4. 4

   Test CANbus and Voltage: Measure voltages and resistance at the DEPR connector. Ensure that the CAN HI and CAN LO signals are communicating at the expected voltage levels.

1. 1

   Resolve Fuel Supply Issues

   If a restriction is found during diagnostics, replace the LPG fuel filter or service the vaporizer to restore proper secondary fuel pressure.

2. 2

   Repair Wiring

   If unseated pins or damaged wires are found at the EPR connector, repair the harness or replace the connector pigtail.

3. 3

   Rebuild or Replace the EPR

   If the fuel supply is unrestricted, the 10A fuse is intact, and all voltage/connectivity checks are normal, the EPR itself has failed.

4. 4

   Installation

   Replace the entire EPR assembly or rebuild it. If rebuilding, disassemble the regulator from the actuator, replace the internal diaphragms, primary/secondary seats, and clamp plate seals using an Impco repair kit, and reassemble.