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Troubleshooting

Aventon Level.2, Pace, Sinch and Aventure: error 21 or W03, motor cuts out on long climbs

An Aventon that shuts off with error 21 or W03 on a long climb is usually the controller protecting itself from too much current or heat. Rest the bike, lower assist, and only suspect parts if it returns on easy rides.

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You're on a long climb with assist turned all the way up, or leaning on the throttle, and the motor shuts off. The display shows 21 or E21, or on some Aventon hub drive bikes a W03 warning. On the Level.2, Pace 350 and Pace 500, Sinch and Aventure, 21 is abnormal current (Level.2 manual, Pace 350 and 500 manual, Sinch manual, Aventure manual), and on the Level.2 and Pace, 26 is overheat protection. Short answer: the controller is protecting itself. E21 usually happens during long climbs at maximum pedal assist, and a 2 minute cool down usually clears it (Aventon E21).

If the code keeps coming back on easy rides, or you smell burning or see melted wiring, stop riding and contact Aventon or a pro. Don't open the controller or motor.

Most likely cause

E21 is the motor's current going past the controller's limit, so the controller shuts down to prevent overheating (Aventon E21). W03 is the same idea for heat: the controller overheated from prolonged heavy use, such as a steep hill at maximum assist or throttle, and cut power to prevent damage (Aventon W03). If either clears after a rest, it was the protection doing its job.

Other causes to rule out

  • A worn cable or poor connection between motor and controller. These are possible causes when E21 persists, and either the motor or controller may need replacing (Aventon E21).
  • Controller damage, which can also trigger W03 (Aventon W03).
  • Brakes rubbing or a heavy load, both causes of reduced range and extra load on the system (Level.2 manual). See e-bike brakes.

How to confirm

  1. For 21 or E21: stop, power off, wait 2 minutes, power on and see if it clears (Aventon E21).
  2. For W03: power off and let the bike cool for about an hour before restarting (Aventon W03).
  3. Note when it happens. Only on long, steep climbs at high assist suggests protection. On flat, easy riding suggests a fault.
  4. If E21 returns, check the motor cable and controller plugs you can reach for damage or looseness with the battery out (Aventon E21). See inspect and clean connectors.

Fix options

Change how you climb (easy)

Since Aventon ties E21 to long climbs at maximum assist and W03 to prolonged heavy use (Aventon E21, Aventon W03), a lower assist level and more pedaling on long hills is the first change to try.

Check tires and brakes (easy)

Low tire pressure and rubbing brakes are drags on the system (Level.2 manual). See set tire pressure.

Reseat the motor cable (easy)

If the code shows up after a wheel removal or a knock to the cable, reseat it. See Aventon error 23 or 24 for the cable checks.

Replace the controller or motor (pro or Aventon)

If E21 or W03 keeps returning on easy rides after a full cool down, the controller or motor may need replacing (Aventon E21, Aventon W03). Contact Aventon for the part, or have a shop diagnose which one.

Parts

  • Controller (through Aventon, only after diagnosis)
  • Rear hub motor (through Aventon, only after diagnosis)

When to get a pro

Sources

Stuck after these checks? Find a shop near you.

Need a pro?

If these steps didn't fix it, find a shop near you in our partner network. For battery or wiring trouble, look for shops marked Battery and electrical.

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