Aventon Bikes with ACU-ECU (Aventon Control Unit) – W120 / W121 Storage & Bluetooth Module Warnings TroubleshootingUpdated 2 days ago
This article explains how to troubleshoot the following warning codes on Aventon bikes equipped with the ACU-ECU (Aventon Control Unit):
- W120 – Storage Fault
- W121 – Bluetooth Hardware Module Disconnect
Use this article if your bike:
- Shows warning code W120 or W121
- Displays storage or Bluetooth hardware warnings
- Experiences Bluetooth connection issues
- Experiences intermittent ECU communication issues
If you are unsure about any step or notice anything unsafe, stop troubleshooting and contact support.
Before You Start
Please prepare the following:
- order number
- Aventon model
- photo or video of the issue
- photo of the warning code
- when the issue first appeared
- whether the bike powers on
- whether the battery charges
- whether the display turns on
- whether the motor engages
- whether the issue happened after charging, riding, transport, storage, water exposure, crash, impact, modification, or third-party repair
- photos of any visible damage
Safety Warnings
- Do not continue riding if the bike has visible damage, overheating, smoke, burning smell, water exposure, motor resistance, or persistent warning codes.
- 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 These Warning Codes Mean
These warning codes indicate a storage or Bluetooth hardware communication issue within the ECU system.
- W120 indicates a storage fault.
- W121 indicates the Bluetooth hardware module is disconnected.
Possible Causes
- data corruption may be present and may automatically repair after restarting
- bug in the current ECU software version
- damaged ECU
- damaged Bluetooth hardware module
Troubleshooting Steps
Step 1 – Power Cycle the Bike
Power off the bike completely.
Wait 10 seconds.
Power the bike back on and check whether the warning code remains.
If the issue clears
The issue may have been caused by temporary data corruption or a startup communication interruption. Monitor the bike during future rides.
If the issue remains
Update the ECU software to the latest version using the Aventon app.
Step 2 – Update the ECU Software
Update the ECU software to the latest version using the Aventon app.
After the update completes, restart the bike and check whether the warning code remains.
If the issue clears
The issue was likely caused by an ECU software bug.
If the issue remains
Replace the ECU following the ECU replacement procedure.
Step 3 – Replace the ECU
If the warning code still remains after updating the ECU software, the ECU may be faulty.
Replace the ECU following the ECU replacement procedure.
If the issue clears
The issue was likely caused by a faulty ECU or Bluetooth hardware module.
If the issue remains
Please contact support for further diagnosis.
When To Contact Support
Please contact support if:
- the warning code remains after completing the steps above
- there is visible damage
- the bike does not power on
- the display does not power on
- the motor does not engage
- the issue appears related to the ECU, Bluetooth hardware module, or internal wiring
- 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
- you need warranty, repair, replacement part, refund, or replacement support
If the issue remains after this step, please contact our support team and include the photos/videos listed below.
What To Send Support
Please send:
- order number
- Aventon model
- photo or video of the warning code
- photo of the display
- photo of the battery area
- photos of visible damage
- confirmation of whether the bike powers on
- confirmation of whether the battery charges
- confirmation of whether the display turns on
- confirmation of whether the motor engages
- confirmation of whether there was water exposure, crash, impact, modification, or third-party repair
- list of troubleshooting steps already completed
Important Safety Notes
- Do not continue riding if the warning code remains.
- Do not ride if there is visible damage, overheating, smoke, burning smell, water exposure, or motor resistance.
- Do not open the battery, controller, ECU, Bluetooth module, 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.