Bafang Error Codes Complete Troubleshooting Guide 2026

If your Bafang motor flashes an error code, start with two quick checks: turn the battery off and on again, then reseat the display cable where it plugs into the frame or motor. This clears roughly half of all error codes on the first try. The table below lists the most common codes, what they mean, and the first thing to do. If the code returns after a reset, follow the detailed steps for that code.

Before You Panic: Two Quick Checks That Fix Most Codes

1. Cycle the battery. Turn the battery off using its switch or remove the key, wait 10 seconds, then power back on. Many error codes (especially 6, 21, and 30) are temporary glitches that clear with a power cycle.

2. Inspect the display cable. The cable from the display to the controller is the most common failure point on Bafang systems. Unplug it at both ends (display and controller), look for bent pins or dirt, then plug it back in until you hear a firm click. If the cable was loose, the code should disappear.

If neither step clears the code, or if the code returns immediately after riding a few feet, move to the appropriate error below.

Detailed Troubleshooting by Error Code

Error 4 – Throttle Voltage Out of Range (M-Series)

Error 4 means the throttle signal voltage is outside the normal 1.0–4.2V range. Unplug the throttle from the controller harness. If the code disappears, the throttle is faulty—replace it with a genuine Bafang unit. Third-party throttles often trigger code 4.

If the code stays with the throttle unplugged, the controller’s 5V voltage regulator may be damaged. Check for melted or corroded pins inside the controller connector. If you see damage, replace the controller rather than attempting to repair the regulator.

Error 6 – Low Battery Voltage

This error triggers when battery voltage drops below the controller’s cutoff threshold (typically 30–32V on a 36V system). Don’t assume the battery is simply drained. Use a multimeter to measure voltage at the battery’s discharge port.

• If voltage is below cutoff but the battery was recently charged, the BMS may have tripped into protection mode. Briefly connect a 10-ohm resistor between the charging port’s positive and negative terminals to wake the BMS. A battery reset tool works too. After resetting, charge the battery fully.
• If voltage is normal (e.g., 36–42V) but error 6 persists, the voltage detection wires inside the controller may be damaged. Inspect the thin wires from the controller’s battery input for breaks or corrosion.

Error 7 – Motor Hall Sensor Fault

Hall sensors tell the controller the rotor position. A single bad sensor usually causes a jerky start or no start at all.

First step: Unplug the motor phase and hall connectors. Look for bent or pushed-back pins. Reseat firmly. If the error clears and stays gone, you’re done.

Branch point: If the error clears after re-seating but returns after riding a mile or two, one of the three hall sensors inside the motor is failing. This requires opening the motor side cover—a job that’s easier with a gear puller for the clutch and a spare gasket. Many shops charge $60–$100 to replace all three sensors at once. If you open the motor, look for visible damage (burnt sensor, broken wires) and replace all three hall sensors (US1 through US3) as a set.

Error 10 – Battery Over-Temperature

Bafang controllers shut down when battery temperature exceeds about 140°F (60°C). This most often happens on a hot summer day while climbing a long hill. Let the battery cool in the shade until it’s below 90°F before reconnecting.

If error 10 appears when the battery feels cool to the touch, the NTC thermistor inside the battery pack may be shorted. Measure resistance between the temperature pin and the negative terminal on the battery’s BMS connector. At 77°F (25°C) it should read about 10kΩ. A reading near zero or infinite means the thermistor is defective—the battery needs professional repair or BMS replacement.

Error 14 – Torque Sensor (Speed Sensor) Fault

This error usually trips when the magnetic disc on the bottom bracket gets dirty or out of alignment. Remove the disc (it’s a plastic ring with magnets), clean it with isopropyl alcohol, and reinstall it so the gap between the disc and the sensor head is no more than 3 mm.

If the error persists, inspect the sensor harness where it runs near the bottom bracket. Chafing against the frame can expose wires. If you find bare copper, tape the damage securely or replace the harness. A new sensor assembly costs about $15–$25.

Error 21 – Speed Sensor Missing Signal

The wheel magnet must pass within 1–3 mm of the sensor on every revolution. Check that the magnet is still glued to the spoke and hasn’t rotated out of alignment. Rotate the wheel slowly while watching the display—if speed shows zero, the sensor wire likely broke inside the insulation near the dropout (a common failure point).

Do not attempt to splice the tiny wires—replace the entire sensor assembly ($10–$15). When installing the new sensor, leave a small loop in the wire near the dropout to prevent future strain.

Error 24 – Controller Over-Current

Error 24 means the controller is drawing more than its rated amperage. Common causes: a short in the motor phase wires, a stalled motor (e.g., from a chain jam or seized bearing), or a faulty controller.

Test: Unplug the three motor phase wires from the controller. Turn the rear wheel by hand. If error 24 goes away, the motor is shorted internally. If the error stays with the phase wires unplugged, the controller itself is damaged. Swap in a known-good controller to confirm before buying a $100+ replacement. Always check the motor connector pins for melting—evidence of a past short.

Error 30 – Communication Error (Display to Controller)

The display and controller communicate over a 5V data line. Error 30 often appears after a fall that knocks the cable loose. Reseat both ends of the display cable (at the display and at the controller). If that fails, try a different display (if available) to see if the controller’s data port is dead.

Some older Bafang displays need a firmware update to fix intermittent error 30. Check your display model number on the manufacturer’s website for update files and use the Bafang programming cable with the Bafang Config Tool (Windows only). If the display is not recognized, the controller’s data port may have failed—replace the controller.

When to Stop Troubleshooting and Call a Pro

Some problems are best left to a shop, especially if you’ve already tried the fixes above and the error returns.

• Melted or corroded internal connectors inside the motor or controller – opening the motor without a proper gasket often leads to water ingress later.
• Battery error codes (6 or 10) that don’t clear after a BMS reset – internal cell damage or a failed BMS requires professional disassembly and testing.
• Water damage visible inside the motor (rust, white corrosion on windings) – a full motor rebuild or replacement is needed.
• Controller failure that persists after swapping – if you can’t find a short, the controller is toast and cannot be serviced.

If you’re unsure about opening high-voltage battery packs or motor housings, spend the shop fee to avoid a fire risk or permanent damage.

FAQ

How to clear Bafang error code?

Turn the battery off and on again. If that doesn’t work, disconnect the battery for 2 minutes, then power up. For persistent codes, address the root cause using the detailed steps above. There is no universal button sequence that clears all Bafang errors.

What are the common problems with Bafang motors?

The three most frequent issues are: (1) loose or corroded display cables (error 30), (2) water ingress into motor hall sensor connections (error 7), and (3) speed sensor misalignment after a wheel change (error 21). All three are easy to fix at home with basic tools.

How do you reset the Bafang ebike?

A full reset involves turning off the battery, removing the display, unplugging the main harness from the controller, waiting 60 seconds, then reassembling in reverse order. This clears stored fault codes. Bafang does not support a factory reset via button combinations on the display.

What is error 4 on Bafang motor?

Error 4 signals a throttle voltage out of the expected 1.0–4.2V range. Unplug the throttle to isolate the problem. If the code clears, replace the throttle. If it stays, the controller’s 5V supply is likely damaged and needs replacing.