This article explains how to troubleshoot the E33 ECU Communication Error on Aventon eBikes fitted with an ACU/ECU (Aventon Control Unit).

Use this article if your bike:

• Shows an E33 error code
• Has display communication issues
• Cannot communicate correctly with the ECU
• Has intermittent display or system connection problems

If you are unsure whether your bike uses an ACU/ECU system, please confirm your Aventon 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 E33 error code
• Photo of the display
• Photo of accessible ECU and display connectors
• Screenshot of the Aventon App firmware version, if available
• When the issue first appeared
• Whether the bike powers on
• Whether the display turns on
• Whether the bike connects to the Aventon App
• Whether the issue happened after charging, transport, storage, water exposure, crash, impact, modification, firmware update, 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 disconnect the battery or power off the bike during firmware updates.
• 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 E33 ECU Communication Error means the ECU is not communicating correctly with the display.

This may happen if:

• There is a poor connection between the ECU and display
• The display or display harness is damaged
• The ECU firmware is outdated
• There is cable or connector damage

Possible Causes

Possible causes include:

• Poor ECU-to-display connection
• Outdated ECU software
• Damaged display
• Damaged display harness
• Worn cable
• Broken connector
• Internal open circuit
• Visible cable or connector damage
• ECU communication issue

Troubleshooting Steps

Step 1 – Inspect and Reconnect the ECU and Display Harness

Turn the bike off before continuing.

Disconnect, inspect, clean, and fully reconnect the accessible:

• ECU connection
• Display connection
• Display harness

Check for:

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

Update the firmware to the latest version using the Aventon App if available.

Restart the bike and check whether the E33 error remains.

If yes – Visible damage is found

Continue to the relevant section below:

• Display harness damage
• Display damage

If no – No visible damage is found

Confirm the ECU software is updated to the latest version using the Aventon App.

Restart the bike and check whether the E33 error remains.

If the issue clears

The issue was likely caused by a loose connection or outdated firmware.

Monitor the bike during normal use.

If the issue remains

Continue to Step 2.

Step 2 – Confirm the ECU Software Is Updated

Using the Aventon App:

• Check for ECU software updates
• Install all available ECU firmware updates

Allow the update process to complete fully.

Restart the bike after updating.

If yes – The E33 error still appears

Continue to Step 3.

If no – The error clears

The issue was likely caused by outdated ECU software.

Continue monitoring the bike during normal use.

If the issue clears

Continue normal use and monitor the bike.

If the issue remains

Continue to Step 3.

Visible Damage Troubleshooting

Step 3 – Display Harness Damage Found

Inspect the accessible display harness 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 harness and connectors.

If the issue remains

The display or ECU system may also require further inspection.

Please contact support.

Step 4 – Display Damage Found

Inspect the display for:

• Cracked screen
• Physical damage
• Water exposure
• Loose wiring
• Broken mounting points

If yes

Do not continue riding the bike.

Please contact our support team with photos of the display and error code.

If the issue remains

The display harness or ECU system may also be affected.

Please contact support.

Step 5 – Check Whether the Error Persists

After reconnecting the system and updating the ECU software, restart the bike and check whether:

• The display operates normally
• The bike connects to the Aventon App
• The E33 error returns

If yes – The E33 error still appears

The issue may involve:

• The display
• Display communication
• The display harness
• The ECU 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 a temporary communication or firmware issue.

Continue monitoring the bike during use.

Step 6 – Check ECU Communication

Check whether:

• The display powers on normally
• The bike stays connected to the Aventon App
• Firmware updates complete successfully
• The E33 error returns repeatedly

If yes – Problems continue

The issue may involve:

• ECU communication
• Firmware communication
• Display communication
• ECU system operation

Please contact our support team with:

• Screenshots of firmware updates
• Photos of the display and error code
• Photos of accessible connectors and wiring

If no – Everything operates normally

The issue was likely resolved during reconnection or updating.

Continue monitoring the bike during use.

When To Contact Support

Please contact support if:

• The E33 error remains after completing these checks
• The bike does not connect correctly to the Aventon App
• Firmware updates fail repeatedly
• The display does not turn on
• There is visible cable or connector damage
• The bike has been exposed to water, crash, impact, transport damage, modification, firmware issues, 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 E33 error code
• Photo of the display
• Photo of accessible ECU and display connectors
• Screenshot of the Aventon App firmware version
• Photos of visible damage
• Confirmation of whether the bike powers on
• Confirmation of whether the display turns on
• Confirmation of whether the bike connects to the Aventon App
• Confirmation of whether firmware updates complete successfully
• Confirmation of whether the issue happened after water exposure, crash, impact, modification, firmware update, or third-party repair
• Confirmation of the troubleshooting steps already completed

Important Safety Notes

• Do not continue riding if the E33 error remains.
• Do not disconnect the battery or power off the bike during firmware updates.
• Do not use the bike if there is visible damage, overheating, smoke, or a burning smell.
• Do not open the ECU, controller, display, battery, 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.