Yale 110-4 – Engine Control Module (ECM) / Engine/Fuel ECU: Coolant Temperature Sensor OORL

The sensor signal voltage has dropped below the acceptable minimum threshold (for example, less than 0.2V on Yanmar engines). The underlying condition is typically caused by the sensor signal being shorted to the sensor ground, shorted to the frame ground, an open wiring circuit, an internal failure of the sensor itself, or a functional failure within the controller's input circuitry.

• Yale and Hyster Forklifts
• Yale internal combustion forklifts (2005+)
• Hyster internal combustion forklifts (2005+)
• Yale VX series
• Yale GC/GLP/GDP 135VX to 360VX

1. 1

   Visually inspect the coolant temperature sensor, its connector, and the wire harness for physical damage, corrosion, or loose connections.

2. 2

   Use a multimeter to test the wiring harness for continuity and check for any shorts to ground or shorts to power.

3. 3

   Use a diagnostic handset or software to check the sensor signal voltages to confirm if the input is reading below the threshold.

1. 1

   Power down and prepare forklift

   Power down the forklift, engage the parking brake, and disconnect the battery ground cable to ensure safety. Allow the engine and coolant to cool completely.

2. 2

   Inspect and clean sensor connection

   Disconnect the coolant temperature sensor. Clean any corroded connectors and re-seat the connection to see if a poor contact was causing the low voltage reading.

3. 3

   Repair or replace wiring harness

   If the wiring harness is damaged or shorting to the frame/sensor ground, repair or replace the affected section of the wiring harness.

4. 4

   Replace coolant temperature sensor

   If the wiring tests good but the sensor is internally shorted or failed, replace the coolant temperature sensor. (You may need to drain a small amount of coolant to prevent spillage during removal).

5. 5

   Test and replace controller

   If the sensor and wiring are both fully functional, the issue may lie within the controller. Test the controller's sensor input circuitry; if it is malfunctioning, the engine controller/ECU will need to be replaced.

6. 6

   Finalize repair and clear codes

   Reconnect the battery, top off any lost coolant, and use a diagnostic tool to clear the fault codes from the system.