Aventon Bikes with ACU-ECU (Aventon Control Unit) – W108 / W109 Bike Lock Failed 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):
- W108 – Bike Lock Failed
- W109 – Bike Lock Failed
Use this article if your bike:
- Shows warning code W108 or W109
- Displays “Bike Lock Failed”
- Cannot properly engage or disengage the bike lock
- Has a kickstand lock or hub lock issue
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 the bike lock system failed to engage or disengage correctly.
The issue may involve:
- the bike being in motion
- an obstructed lock mechanism
- incorrect lock positioning
- controller issues
- bike lock hardware issues
Possible Causes
- the bike is in motion
- the lock is blocked
- the lock position is incorrect
- bug in the current ECU software version
- damaged bike lock
- damaged ECU
- disconnected controller
- damaged controller
Troubleshooting Steps
Step 1 – Check the Bike Lock Position
Ensure the bike is completely stopped and the lock mechanism is unobstructed.
Kickstand Lock
Lower the kickstand to the proper position, then reengage the lock.
Hub Lock
Rock the bike forward and backward, then reengage the lock.
After completing the adjustment, check whether the W108 or W109 warning remains.
If the issue clears
The issue was likely caused by incorrect lock positioning or lock obstruction.
If the issue remains
Inspect the controller for visible damage or disconnection.
Step 2 – Inspect the Controller
Inspect the controller for:
- visible damage
- loose connections
- disconnected wiring
If the controller is damaged
Replace the controller.
After replacement, restart the bike and check whether the warning remains.
If the controller is disconnected
Reconnect the controller.
After reconnecting the controller, restart the bike and check whether the warning remains.
If no visible controller issue is found
Update the ACU software to the latest version using the Aventon app.
If the issue clears
The issue was likely caused by a controller connection issue.
If the issue remains
Update the ACU software to the latest version using the Aventon app.
Step 3 – Update the ACU Software
Update the ACU software to the latest version using the Aventon app.
After the update completes, restart the bike and check whether the warning remains.
If the issue clears
The issue was likely caused by an ACU software bug.
If the issue remains
Replace the bike lock assembly.
Step 4 – Replace the Bike Lock Assembly
Replace the bike lock assembly.
After replacement, restart the bike and check whether the warning remains.
If the issue clears
The issue was likely caused by a faulty bike lock assembly.
If the issue remains
Replace the ACU.
Step 5 – Replace the ACU
If the warning still remains after replacing the bike lock assembly, the ACU may be faulty.
Replace the ACU following the ACU replacement procedure.
If the issue clears
The issue was likely caused by a faulty ACU.
If the issue remains
Please contact support for further diagnosis.
When To Contact Support
Please contact support if:
- the W108 or W109 warning 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 controller, bike lock system, ACU, 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 the bike lock mechanism
- 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, ACU, 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.