Bosch Oven Error Code E309
E309 mirrors E009 but in the main control module instead of the display: the module's start-up memory check failed and all heating elements are disabled. A check that passes on the next start-up clears it; a persistent E309 means a new control module.
Common causes
- Control module firmware/memory check failed
- Control module hardware failure
- Communication loss at start-up corrupting the check
What to check, in order
- Reset the oven at the breaker for a minute: the ROM check re-runs at start-up and cancels the error if it passes this time.
- If E309 appears at every start-up, the control module is not recovering.
- There are no user-serviceable parts for this code; note whether the display (user interface) still works normally, which helps the technician separate the two boards.
- Book a technician: the fix is a control module replacement.
Clear the code and test
- Fix what the checks above found first. Clearing the code without fixing the cause only brings it back.
- Plug the appliance back in and restore its water supply if it has one.
- Run the shortest programme and watch the point where the code appeared before.
- If the programme finishes with no code, the fault is cleared. If the code returns, write it down before calling a technician — it speeds up the diagnosis.
When to call a professional
This code usually points to a faulty part, wiring or the control board on a Bosch oven. Run the checks above to rule out the simple causes, then book a technician — and book one straight away if any of these apply:
- The code comes back after you have run the checks and a test cycle.
- You smell burning, see sparks or scorch marks, or the breaker trips.
- Water is leaking and you cannot stop it at the tap.
- The fix needs panels opened beyond what your manual describes, or a part tested with a meter, and you are not set up for that.
When you call, give the brand, the code E309, your model number (on a label inside the door or on the back) and the checks you already ran. It shortens the visit.
Repair or replace?
This fault is in professional territory: the fix usually means a major part or board-level work, and the labour adds up. If your machine is already well into its service life, get the repair quote first, then compare it with the price of a current equivalent model before you decide. Paying a large share of a new machine's price to repair an old one is rarely the better deal; replacing a machine over one cheap fault is wasteful too.
Parts that may be involved
Control module
Parts are model-specific. Find your model number first — usually on a label inside the door, on the door frame or on the back — and match the part to that number before ordering.
Questions people ask about E309
What does E309 mean on a Bosch oven?
E309 means: ROM check error in the control module. E309 mirrors E009 but in the main control module instead of the display: the module's start-up memory check failed and all heating elements are disabled. A check that passes on the next start-up clears it; a persistent E309 means a new control module.
Can I fix Bosch E309 myself?
Only the preliminary checks. Code E309 usually means a part, wiring or the control board has failed, which is a technician job. Run the checks to rule out simple causes before you book.
How do I clear Bosch E309?
Fix the cause first — clearing the code on its own brings it straight back. Then restore power and water, run the shortest programme, and watch the stage where the code appeared. If the programme finishes with no code, it is cleared.
Sources checked
- Bosch Home (US) owner support: dishwasher error codes
- Coolblue advice: Bosch and Siemens washing machine errors
The meaning and checks for this code were checked against the sources above in November 2026. Codes vary by model and region; if your manual lists a different meaning for your exact model, follow the manual.