Guide: Diagnosing and fixing Jungheinrich Error Code 1901

Step 2 – CAN Bus Voltage Test (Key ON, Engine OFF)

Set your multimeter to DC Volts.

• Probe CAN High (usually pin 4 on the diagnostic port) and Ground.
• Probe CAN Low (pin 5) and Ground.
• Expected: CAN High ~ 2.6V; CAN Low ~ 2.4V. If you see 0V or battery voltage (>5V), there is a short or open circuit.
• Resistance test (key OFF, battery disconnected): Measure between CAN High and CAN Low at the diagnostic port. Expected: 60 ohms. If you see 120 ohms, one termination resistor is missing. If you see near 0 ohms, wires are shorted together.

Common causes & fixes

• Loose/corroded connector at display or joystick — clean, secure, replace seal.
• Damaged CAN wiring or broken shield — repair/replace harness; restore shielding and grounds.
• Faulty display/control module — replace module and program with vehicle parameters.
• Low battery or intermittent main supply — charge/replace battery; check power distribution.
• Missing/incorrect termination resistor or short on CAN — restore proper termination, isolate short.

Jungheinrich Error Code 1901: Causes, Troubleshooting, and Reset Guide

Jungheinrich Error Code 1901: Diagnosis and Resolution

Overview On Jungheinrich forklifts and material handling equipment, Error Code 1901 typically indicates a hardware communication fault, specifically related to the vehicle's Controller Area Network (CAN-Bus) system.

In most modern Jungheinrich machines (especially EFG and EJE series), this code signals that a specific control module—usually the Vehicle Controller (VE)—has lost communication with another major component, such as the display interface or a peripheral sensor module.

3. Corroded or Loose Connectors (X1/X2 plugs)

Moisture ingress from wet warehouse floors or pressure washing corrodes the small pins inside the motor connector. Code 1901 often appears after cleaning.

6. Electromagnetic Interference (EMI)

High-current cables (battery to controller) running parallel to CAN bus wires can induce noise. This is rare on modern Jungheinrich trucks due to shielded wiring but can occur after non-OEM repairs or incorrectly routed harnesses.

Step 4 – Swap Test (If available)

If you have access to a known-good used or spare drive controller (same part number), swap it in. Do not swap with a different part number – Jungheinrich controllers are programmed for specific truck models and weight classes.