Yale 51-7 – Engine Control Unit (ECU) or Vehicle System Manager (VSM): Throttle Position Sensor Signals A and B Not At Commanded Value

This code indicates that the throttle position sensors (or accelerator pedal sensors) are outputting incorrect voltage levels, causing a mismatch with the expected values commanded by the system. The system detects that the accelerator pedal sensor and the throttle sensor are not tracking together within the acceptable threshold (typically 15%).

• Yale and Hyster Forklifts
• Yale VX Series
• GDP040VX
• GLP050VX
• GLC050VX
• GC135VX
• Hyster FT Series
• H50FT
• S50FT
• H60FT

1. 1

   Perform a voltage sweep test by accessing the diagnostic display on the dash and monitoring the accelerator pedal sensor for a consistent voltage sweep (typically 1V to 4V) as the pedal is slowly pushed.

2. 2

   Verify the sensor is receiving supply voltage and that there is a valid signal on both the A and B circuits.

3. 3

   Inspect the sensor signal circuits for high resistance, damaged wires, or corroded connectors (especially on Mazda engines).

4. 4

   Inspect the electronic throttle body to see if the mechanism is physically sticky, jammed, or incorrectly adjusted.

1. 1

   Fix Wiring

   If the diagnostic checks reveal damaged or corroded wiring in the sensor signal circuit, repair or replace the affected harness sections.

2. 2

   Clean/Adjust Throttle Body

   If the electronic throttle body is sticky, clean the mechanism and ensure it is correctly adjusted so it can move freely.

3. 3

   Replace Faulty Sensors

   If the accelerator pedal position sensor or the throttle body sensor fails the voltage sweep test (e.g., dead spots, no voltage change, or signals A and B do not match), replace the faulty sensor.

4. 4

   Calibrate

   After installing new sensors, calibrate them to the controller to ensure the ECU recognizes the correct idle and wide-open throttle values.

5. 5

   Controller Update

   If calibration problems persist after replacing the sensors and verifying the wiring, the controller firmware may need to be updated or the controller itself replaced.