This article explains how to troubleshoot the E21 Current Error on an Aventon eBike.

Use this article if your bike:

• Shows an E21 error code
• Loses motor assistance during riding
• Stops assisting during steep climbs or heavy load
• Shows a current or motor-related warning

If you are unsure of your Aventon model, please confirm your model before continuing.

Stop troubleshooting immediately if anything looks unsafe, damaged, overheated, or smells burnt.

Before You Start

Please prepare the following:

• Order number
• Aventon model
• Photo or video of the E21 error code
• Photo of the display
• Photo of the motor cable area
• Photo of visible connectors, if relevant
• When the issue first appeared
• Whether the bike powers on
• Whether the display turns on
• Whether the motor engages
• Whether the issue happened during climbing, heavy riding load, transport, storage, water exposure, crash, impact, modification, or third-party repair
• Photos of visible damage

Safety Warnings

• Do not continue riding if the bike has visible damage, overheating, smoke, or a burning smell.
• Do not open sealed electrical components.
• Do not work on wiring while the bike is powered on or charging.
• Stop and contact support if you are unsure.

What This Error Means

The E21 Current Error means the motor current output exceeded the controller’s current limit.

This can cause the controller to temporarily shut down to protect the system from overheating.

This may happen during long climbing periods with maximum pedal assist engaged.

The error may also indicate damage to the motor or controller system.

Possible Causes

Possible causes include:

• High motor load during climbing
• Controller overheating protection
• Damaged motor cable
• Damaged controller cable
• Worn cable
• Broken connector
• Internal open circuit
• Damaged motor
• Damaged controller
• Visible cable or connector damage

Troubleshooting Steps

Step 1 – Inspect the Motor and Controller Cables

Turn the bike off before continuing.

Disconnect, inspect, and clean the accessible motor cable and controller cable connections.

Check for:

• Loose connectors
• Dirt or contamination
• Bent pins
• Worn cables
• Visible damage
• Broken connectors

If yes – Visible damage is found

Do not continue riding the bike.

Please contact our support team with photos of the damaged cable or connector.

If no – No visible damage is found

Reconnect the cable securely.

Allow the bike to cool down for 1 hour.

After cooling:

• Ride the bike on flat ground only
• Ride for approximately 1–2 miles
• Check whether the E21 error returns

If the issue clears

The issue was likely caused by temporary controller overheating from high motor load.

Monitor the bike during future riding, especially during steep climbs or prolonged high assist use.

If the issue remains

Continue to Step 2.

Step 2 – Check Whether the Error Persists

After reconnecting the cables and allowing the bike to cool down, restart the bike and test ride on flat ground.

If yes – The E21 code still appears

The issue may involve the motor or controller system.

Please contact our support team with the photos/videos listed below so we can review the next step.

If no – The error no longer appears

The issue was likely caused by temporary overheating or a poor cable connection.

Continue monitoring the bike during riding.

Visible Damage Troubleshooting

Step 3 – Motor Cable or Connector Damage Found

Inspect the accessible motor cable and connector area for:

• Cuts
• Worn insulation
• Pinched cables
• Loose connectors
• Bent pins
• Broken fittings

If yes

Do not continue riding the bike.

Please contact our support team with photos of the damaged area.

If the issue remains

The motor or controller system may require further inspection.

Please contact support.

Step 4 – Motor-Related Symptoms Continue

Check whether:

• The motor does not engage
• Motor assistance cuts in and out
• The E21 error returns repeatedly after cooling and reconnecting the cables

If yes

The motor system may require further inspection.

Please contact our support team with:

• Video of the issue
• Video of the display during riding
• Photos of the motor cable and connector

If the issue remains

Please contact support.

Step 5 – Controller-Related Symptoms Continue

Check whether:

• The bike powers on but motor assistance does not work
• The E21 error appears immediately after startup
• The issue continues after the bike cools down

If yes

The controller system may require further inspection.

Please contact our support team with:

• Photo of the display
• Video showing the E21 error
• Photos of accessible cables and connectors

If the issue remains

Please contact support.

When To Contact Support

Please contact support if:

• The E21 error remains after completing these checks
• The motor does not engage
• Motor assistance cuts out repeatedly
• There is visible cable or connector damage
• The bike overheats repeatedly
• The bike has been exposed to water, crash, impact, transport damage, modification, or third-party repair
• You are unsure how to safely complete a step

If the issue remains after these steps, please contact our support team and include the photos/videos listed below.

What To Send Support

Please send:

• Order number
• Aventon model
• Photo/video of the E21 error code
• Photo of the display
• Video showing the motor issue, if possible
• Photo of the motor cable area
• Photo of accessible connectors, if safe
• Photos of visible damage
• Confirmation of whether the bike powers on
• Confirmation of whether the display turns on
• Confirmation of whether the motor engages
• Confirmation of whether the issue happened during climbing, heavy assist use, transport, water exposure, crash, impact, modification, or third-party repair
• Confirmation of the troubleshooting steps already completed

Important Safety Notes

• Do not continue riding if the E21 error remains.
• Do not ride the bike if there is visible damage, overheating, smoke, or a burning smell.
• Do not open the motor, controller, or sealed electrical components.
• Do not force connectors.
• Do not work on wiring while the bike is powered on or connected to the charger.
• Contact support if you are unsure.