Yale 51-2 – Controller / ECU (Engine Control Unit) or VSM (Vehicle System Manager): Throttle Position Sensor Signals A and B Not Tracking Correctly

The dual signals (A and B) generated by the Throttle Position Sensor (TPS) or Accelerator Pedal Position Sensor are not correlating or moving together as expected by the system. This is typically caused by sensor misalignment or physical wear, wiring damage, a sticky Electronic Throttle Assembly (ETA) or incorrectly adjusted throttle mechanism, or calibration errors.

• Yale and Hyster Forklifts
• Yale Veracitor series (e.g., GLC050, GLC/GLP/GDP 030-155VX series)
• Yale ERP series (e.g., ERP030 TF)
• Hyster Fortis series (e.g., S50FT, H80, H40-70FT)

1. 1

   Inspect the pedal assembly and shaft for looseness or worn bushings that can throw the sensor out of physical adjustment.

2. 2

   Inspect the wiring harness and connectors at the throttle body and pedal sensor, giving wires a firm tug to check for internal breaks.

3. 3

   Check the electronic throttle body for stickiness or dust buildup.

4. 4

   Test the sensor voltage sweep using an analog multimeter to spot sudden blips or dead spots as the pedal is depressed.

5. 5

   Ensure the frame ground is clean and secure, scraping away any paint to ensure bare metal contact.

1. 1

   Clean and Re-adjust

   If the sensor is simply dirty or misaligned, clean the throttle body and re-adjust the input shaft to the pedal.

2. 2

   Replace the Sensor/Pedal

   If physical wear (bad bushings) or internal sensor failure is confirmed, replace the Throttle Position Sensor or the entire Accelerator Pedal Assembly.

3. 3

   Calibrate the New Sensor

   Every 'drive-by-wire' system requires re-calibration when replacing the TPS, pedal assembly, or any other component in the system. If you do not calibrate the new component via the controller, the 51-2 error will persist.

4. 4

   Controller Replacement

   If the hardware, wiring, and calibration are all verified to be fine but the code remains, test and replace the ECU/Controller module as a last resort.