Is error 25 different from error 26?

Error 25 is a general torque sensor signal fault. Error 26 is specifically a torque sensor speed signal fault — it relates to the cadence component within the torque sensor assembly rather than the force measurement itself. Both errors indicate a torque sensor issue and the diagnosis approach is the same.

Bafang E-Bike Error 25: Torque Sensor Fault Fix

What Error 25 Means

Error 25 on Bafang M-series motors (M500, M600, M420) and some BBS-series configurations signals that the torque sensor is not providing valid data to the controller. Bafang mid-drive motors with torque sensing measure the force applied to the pedals via a strain gauge in the bottom bracket area. When this sensor returns out-of-range or absent data, error 25 is raised and pedal-assist output is disabled or degraded.

Note: Bafang BBS01 and BBS02 systems with cadence-only sensing (no torque sensor) cannot produce error 25. This error is specific to torque-sensing configurations.

Common Causes

Damaged torque sensor cable at bottom bracket — The cable routing through or around the bottom bracket shell is vulnerable to pinching during bottom bracket installation or from frame flex. This is the most common cause of error 25 on M-series motors.
Loose torque sensor connector — The connector between the torque sensor and the main motor harness has worked loose or corroded.
Bottom bracket over-torque — Installing the bottom bracket with excessive torque can compress the sensor element beyond its measurement range, causing permanent offset errors.
Water ingress at sensor — Moisture in the bottom bracket shell reaching the torque sensor element or its connector causes resistance measurement drift.
Worn or failed sensor element — After high mileage, the strain gauge element can develop micro-cracks causing signal loss or drift.

Fix Procedure

Step 1: Power Cycle

Power off, wait 30 seconds, power on. Error 25 caused by a startup calibration miss (starting with pressure on pedals) clears after a power cycle.

Step 2: Inspect the Torque Sensor Cable Route

On M-series motors, the torque sensor cable routes from the sensor in the bottom bracket area to a connector near the motor body. Follow the cable carefully and look for any section that appears pinched, kinked, or shows abrasion marks where it passes through frame guides or around the bottom bracket shell.

Step 3: Check and Clean the Connector

Locate the torque sensor connector — typically a small waterproof JST-style connector near the motor or bottom bracket. Disconnect, spray with contact cleaner, dry, and reconnect. Corrosion on these small pins is a frequent cause of intermittent error 25.

Step 4: Check Bottom Bracket Torque

If the bottom bracket was recently installed or removed, verify the installation torque matches the Bafang specification. Re-installing the BB to specification and recalibrating resolves error 25 in cases where over-torque caused sensor compression.

Bafang E-Bike Error Code 25: Torque Sensor Fault