Chinese hub motor (Aikema, MXUS, Bafang, Gobao…): diagnosing Halls, phases and gears with a multimeter

The vast majority of budget Chinese e-bikes have their motor in the hub of the rear wheel, sometimes the front. On the casing you sometimes read a name: Aikema, Bafang, MXUS, Dapu, Ananda, or more and more often nothing at all. Good news: whatever the maker, a hub motor is diagnosed the same way, because it is built the same way. Three sensors, three phases, and on many models a gear reduction.

First: who makes what

• Aikema: a motor maker based in Suzhou, which claims to have been founded in 1986 and produces hub motors, mid-drives, controllers and displays. Its small geared motors (the Q100H and Q128H are examples well known to home builders) power many kits and e-bikes.
• Bafang: best known for its mid-drives, it also makes hub motors. Its systems' codes are in our article on Bafang error codes.
• MXUS, Dapu, Ananda: other big Chinese hub-motor suppliers, found on bikes of every brand.
• Gobao: the name gets around, and the brand does exist. It is a Chinese motor maker supplying bike manufacturers (OEM); according to the company, more than twenty years in business and around 1,500 employees. In 2026 it is mostly talked about for a mid-drive, the X1P, shown at Eurobike with a built-in continuously variable transmission (150 Nm, 1,500 W peak), with series production announced for February 2027. We found no public documentation (code table, workshop manual) for Gobao hub motors. If your casing carries that name, the method below applies as is.

Above all, remember this: the motor does not talk. Error codes come from the controller and appear on the screen. To read them, see our articles on Chinese displays and KT controllers. Here we deal with what the code points to: the motor itself.

Geared or direct drive?

This table changes the diagnosis: a geared motor that "spins but drives nothing" almost always has an internal mechanical problem; a direct-drive motor almost never.

Symptoms, and what they point to

Tools

A multimeter costing a few tens of pounds is enough (we explain the basic measurements in the 6 multimeter measurements). Add fine probes or needles to back-probe the connectors, and that is it for the electrical side. To open a geared motor, you also need whatever removes the side cover (screws, sometimes a puller) and patience.

Testing the Hall sensors

The three Hall sensors tell the controller where the rotor is. They connect through a small 5-wire connector (sometimes 6 with a temperature sensor): red (supply, about 5 V), black (ground), and three signals, usually yellow, green, blue.

1. Controller powered, Hall connector plugged in, back-probe the connector.
2. First check about 5 V between red and black. If there is nothing, the problem is on the controller or cable side, not the sensors.
3. Then measure between black and each signal while turning the wheel slowly by hand (in the riding direction for a geared motor, which otherwise just freewheels). Each signal should alternate between about 0 V and about 5 V.
4. A signal stuck at 0 V or 5 V: dead sensor or cut wire. A signal that only reaches half voltage: dubious sensor.

The sensors can be replaced (they are standard components soldered into the stator), but it means opening the motor and soldering cleanly. Many owners prefer to replace the whole motor.

Testing the three phases

The three thick wires (yellow, green, blue, like the Halls but thicker) feed the windings. Battery removed, phase connector unplugged:

• Spin test: turn the wheel by hand with the phases unplugged: it should spin freely. Then join two phases together: on a direct-drive motor, the wheel becomes noticeably harder to turn. Do it for each pair: all three pairs should brake the same. A pair that does not brake points to an open phase. On a geared motor, test in the riding direction, as the internal freewheel hides the effect the other way.
• Voltage test: multimeter on AC volts, measure between each pair of phases while spinning the wheel at a steady speed. The three readings should be close; one very different reading signals a damaged winding.
• Insulation test: between each phase and the axle (or casing), the multimeter should show infinite resistance (OL). A measurable value means a bare wire touching, often at the axle exit, where the cable takes the most abuse.

Phase-to-phase resistance is too low for an ordinary multimeter to measure accurately: use it only to compare the three pairs with each other.

Opening a geared motor

If the electrical tests are fine but the motor spins without driving, or clacks, the inside is to blame. You usually find three planetary gears (often nylon), a ring gear and an internal freewheel. Gears worn or melted after a long overloaded climb, a slipping freewheel: parts exist for common models, provided you identify the motor exactly (casing diameter, tooth count, engraved reference). Use the opportunity to check the magnets and any sign of water. The question then is economic: a rebuild can cost almost as much as a new motor, especially with workshop labour.

Diagnosis: cheapest first

1. Read the code on the display and translate it with the right table.
2. Check the motor connectors (Hall and phases): clean, fully home, properly aligned after removing a wheel.
3. Inspect the cable at the axle exit.
4. Hall test.
5. Phase and insulation test.
6. Listen to and feel the motor freewheeling: noise, tight spot, clack.
7. Open the geared motor.
8. Replace the controller, or the complete motor.

Safety: battery and dropouts

An e-bike lithium battery is not to be opened; remove it before touching the phases. And a point often forgotten on kits: the motor's torque reacts against the axle. On an aluminium fork or dropouts, a powerful motor without a torque arm can spin the axle in the dropout, rip out the motor cable and, at worst, let the wheel come out. If the axle has moved, or the dropout is spread or cracked, the bike stays off the road until repaired.

When to hand it over

A burnt winding (smell, blackened varnish), a damaged dropout, a suspect battery, or simply no wish to solder sensors: a workshop, or a complete replacement motor. To find parts and judge whether the repair is worth it, read repairing a Chinese e-bike and our guide to Chinese e-bike brands.

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A hub motor with no reference at all, measurements that match no case? Ask the assistant with your multimeter readings and the code shown.