Turn the ignition key or log-off the digital keypad to shut down the truck completely.

If you are unable to clear the code by restarting the vehicle, you may need to consult the official Jungheinrich Operating Manuals Database for your specific model series. Machineseeker Blog - pedal voltage readings required for a technician to calibrate the potentiometer? Jungheinrich Forklift Error Codes - Machine Maxx USA

A qualified technician should use a Jungheinrich diagnostic tool to check the "pedal value" in the controller. If the value is not at zero when the pedal is idle, the potentiometer needs adjustment or replacement. 4. Controller Reset Sometimes the error code is "latched" in the memory.

| Step | Action | |------|--------| | 1 | – reset the truck. Does error return immediately? | | 2 | Inspect the drive controller connector (usually under the cover near the drive motor). Look for green/white corrosion, bent pins, or moisture. | | 3 | Unplug and reseat the small CAN connector (not the large motor power cables). Listen for a click. | | 4 | Check the main battery connections – loose or dirty terminals can cause CAN voltage dips. | | 5 | If the truck has been pressure washed , suspect water inside a controller or connector. |

At its core, error 1901 indicates that the drive controller is receiving inconsistent or invalid data from the tiller head. In modern Jungheinrich equipment, the tiller communicates via a CAN-bus (Controller Area Network) system. If the digital heartbeat between the control handle and the motor controller is interrupted, the machine triggers 1901 to prevent unintended movement. This is most often caused by a break in the wiring harness, a failed tiller sensor, or a software handshake error. Common Symptoms of Error 1901

Follow this progressive troubleshooting process to clear the code and return your material handling equipment to service.

The operator is resting their foot on the pedal while turning the key. The accelerator pedal is stuck down due to debris.

Look beneath the floorboard mat surrounding the base of the pedal assembly.

For safety reasons, Jungheinrich forklifts are designed not to operate if the operator is already pushing down on the accelerator pedal when the key is turned on. This prevents the truck from abruptly driving off upon ignition. The truck does not respond to throttle input. The display panel shows "1901.1".

If the physical pedal is neutral but the code stays, check the sensor electronics using a multimeter or a diagnostic tool like Jungheinrich JET (Judit):

The of your Jungheinrich forklift (e.g., EFG 220, ERE 120)? If any other codes are appearing on the dashboard?

If your Jungheinrich forklift, stacker, or reach truck is displaying this error code, it typically indicates a safety-related issue that prevents the machine from starting. Here is a comprehensive guide to understanding, troubleshooting, and clearing this code. What is Jungheinrich Error Code 1901.1?

: The accelerator pedal was already pressed down when the ignition key was turned or the truck was started.

Problems with the hydraulic fluid level, contamination of the hydraulic fluid, or malfunctioning hydraulic components can trigger this error code.