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Curtis Code 23
Undervoltage Cutback — controllers 1234 / 1236 / 1238

Possible causes (from the Curtis manual)

1. Normal operation. Fault shows that the batteries need recharging. Controller is performance limited at this voltage. 2. Battery parameters are misadjusted. 3. Non-controller system drain on battery. 4. Battery resistance too high. 5. Battery disconnected while driving. 6. See Monitor menu » Battery: Capacitor Voltage. 7. Blown B+ fuse or main contactor did not close.

When it sets / how it clears

Set: Capacitor bank voltage dropped below the Undervoltage limit (see page 55) with the FET bridge enabled. Clear: Bring capacitor voltage above the Undervoltage limit.

Effect of the fault

Reduced drive torque.

Curtis 1234/1236/1238 controllers are fitted to many electric forklifts and industrial trucks (including models from Chinese brands that use Curtis control). If your display shows code 23 with a Curtis controller, this entry applies; the vehicle maker’s manual may add model-specific notes.

Need the part?

For controller, contactor, sensor or throttle parts, send us the code (Curtis 23), controller model and vehicle model on WhatsApp — we quote genuine and OEM parts for export.

Source: Curtis 1234/36/38 Controller Manual, OS 11, Section 8 Diagnostics & Troubleshooting, Table 5. Compiled 2026-10-29. No affiliation with Curtis Instruments.