- Electric mobility
- Electric bicycle
120109
Bosch eBike 120109: The LEDs on your control unit are not working.
Risk level
High
Professional inspection is recommended.
Urgency
Immediate
Quick answer
The LEDs on your control unit are not working. This may mean that no motor support is available to you, and your eBike switches off. For 120109, Bosch's user step is: Restart your eBike. If the problem persists, please contact your specialist dealer. If the same code returns, preserve the display and stop repeating resets.
Safety first
Stop and check this first
- Do not open powered components or bypass sensors. Stop riding if assistance, braking, lighting or controls behave unpredictably, or if there is heat, smell, damage or moisture.
Safe checks you can perform
- Preserve the code before changing anything
- Apply only Bosch's published user step
- Use recurrence as the stop point
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measured handoff for 120109
What a technician must be able to justify
A technician is coming
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Measured handoff for 120109
What they doUse the saved timing, system generation and Bosch diagnostics to test Control unit in the state that produced 120109; verify software, connectors and component values before replacement.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Checks and evidence, step by step
Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
- 1
Preserve the code before changing anything
No special tools
Procedure
Photograph 120109. Record the eBike model, Bosch system generation if known, battery level, Control unit, what stopped working and when the code appeared.
Do not open powered components or bypass sensors. Stop riding if assistance, braking, lighting or controls behave unpredictably, or if there is heat, smell, damage or moisture.
Evidence: Bosch eBike Systems — official fault code 120109
- 2
Apply only Bosch's published user step
No special tools
Procedure
Restart your eBike. If the problem persists, please contact your specialist dealer. Record whether the condition “The LEDs on your control unit are not working.” disappears and whether 120109 reappears after the exact published step. Do not add an undocumented reset or open a component.
Do not open powered components or bypass sensors. Stop riding if assistance, braking, lighting or controls behave unpredictably, or if there is heat, smell, damage or moisture.
Evidence: Bosch eBike Systems — official fault code 120109
- 3
Use recurrence as the stop point
No special tools
Procedure
If 120109 remains absent, monitor the same function; that does not prove a repair. If “The LEDs on your control unit are not working.” or 120109 returns, stop the user checks and book a Bosch eBike specialist.
Do not open powered components or bypass sensors. Stop riding if assistance, braking, lighting or controls behave unpredictably, or if there is heat, smell, damage or moisture.
Evidence: Bosch eBike Systems — official fault code 120109
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Electric mobility
- Brand
- Bosch eBike Systems
- Product type
- Electric bicycle
Known code variants
- Bosch 120109 bici elettrica
- Bosch 120109 bicicleta eléctrica
- Bosch 120109 E-Bike
- Bosch 120109 eBike
- Bosch 120109 vélo électrique
- Bosch eBike code 120109
- Bosch eBike error 120109
- Bosch eBike Fehler 120109
- Bosch eBike Fehlercode 120109
- code Bosch eBike 120109
- codice Bosch eBike 120109
- código Bosch eBike 120109
- erreur Bosch eBike 120109
- error Bosch eBike 120109
- errore Bosch eBike 120109
What it means
Bosch eBike Systems assigns 120109 to Control unit with source severity CRITICAL_ERROR. It reports the detected state, not proof that one particular part has failed. This may mean that no motor support is available to you, and your eBike switches off.
Warnings and stop conditions
- Highsource verified
Do not open powered components or bypass sensors. Stop riding if assistance, braking, lighting or controls behave unpredictably, or if there is heat, smell, damage or moisture.
Evidence: Bosch eBike Systems — official fault code 120109
Symptoms and causes
Probable causes · in order
- What the code establishesConfirmed
Bosch identifies 120109 at Control unit: The LEDs on your control unit are not working. Keep that meaning scoped to a Bosch eBike system and the exact code shown.
Evidence: Bosch eBike Systems — official fault code 120109
- What the official step decidesPossible
If “The LEDs on your control unit are not working.” clears after Bosch's exact step, only the current condition has cleared; no failed part has been proved. If 120109 returns, the documented user branch is exhausted and the recurrence becomes the evidence for service.
Evidence: Bosch eBike Systems — official fault code 120109
Virtual technician
Does 120109 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Bosch eBike Systems — official fault code 120109
Bosch eBike Systems · 2026 · official_doc
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