Yale 91-2 – Controller / Display System Controller (DSC) or Engine ECU: Accelerator Pedal Position Sensor Signals A and B Not Tracking Correctly

This code indicates a correlation error between the dual signals (Signal A and Signal B) generated by the accelerator pedal position sensor. The system expects these two signals to mirror each other within a specific tolerance. When the difference between the two sensor signals goes beyond the allowable tolerance, or if the signals are not synchronized, the system triggers this fault to prevent unintended acceleration.

• Yale and Hyster Forklifts
• Yale VX Series (e.g., GLC050VX)
• Hyster FT Series
• All Engines except Cummins QSB 3.3L

1. 1

   Perform a Soft Reset: Turn the truck power to OFF for no less than 30 seconds, then turn it back to ON to clear the displayed DTC. Check if the code reoccurs.

2. 2

   Conduct a Wiring & Connector Inspection: Turn the power OFF. Conduct a detailed physical inspection of all connectors and wiring associated with the accelerator pedal. Disconnect and reconnect all relevant connectors to ensure they are seated properly and free of corrosion. Repair wiring first if faults are found.

3. 3

   Perform a DSC Voltage Sweep Test: At the DSC, press ENTER to access the Main Menu, scroll to DIAGNOSTICS > ENGINE DATA DISPLAY > ACCELERATOR PEDAL A. Record the baseline voltage and monitor it while pressing the accelerator pedal fully to the stop. The voltage must increase smoothly from approximately 1.0 Vdc to 4.5 Vdc without any interrupts, drops, or skips.

4. 4

   Perform a Mechanical Bushing Check: Start the engine, press the throttle pedal down, and push on it sideways. If the code triggers during this lateral movement, the bushings inside the pedal assembly are worn out.

1. 1

   Power off truck

   Ensure the truck power is completely OFF.

2. 2

   Remove faulty component

   Remove the faulty Accelerator Pedal Position Sensor. Note: If the pedal bushings were found to be worn during the mechanical check, you will need to replace the entire pedal and mount assembly, not just the sensor.

3. 3

   Install new component

   Install the new sensor/pedal assembly. Do not discard the original sensor until the repair is fully verified.

4. 4

   Secure wiring connections

   Ensure that all wiring harness connections are completely and securely inserted into the new component.

5. 5

   Test throttle response

   Turn the truck power ON and test throttle response.

6. 6

   Check controller connections

   If the sensor tests perfectly fine but the code persists, check for a 'Functional Failure in Controller.' Ensure all connections to the main controller are fully seated, leave power OFF for 30 seconds, and re-test.