When a Bosch oven throws Error Code E305, it’s telling you the control system isn’t seeing a proper link between the “baseplates” (the key boards/modules that talk to each other and run heat, fans, and safety checks). That sounds serious, but in many kitchens this shows up after a brief power dip, a slammed breaker, or a momentary communication glitch—so don’t panic.

The quickest first move is a clean power reset

Turn the oven off, then switch the circuit breaker off as well. Give it a few minutes so any residual charge can bleed down and the boards fully reboot, then bring power back on and start the oven as usual. If the message was caused by a one-off communication hiccup, E305 usually clears and you’re back to normal cooking.

If the code returns, pay attention to behavior: does the oven heat and then stop, or refuse to start at all? Intermittent E305 during preheat can point to a loose connector, heat-soaked wiring, or a failing board that only misbehaves when hot. A code that pops up instantly on power-up can indicate a persistent communication fault between modules, a damaged harness, or a board that isn’t booting. You might also notice the cooling fan cycling oddly or the display lagging—more small signs that the boards aren’t talking cleanly.

At this stage it’s wise to bring in a technician. The fix often involves pulling the unit forward, removing the top panel, and checking harness plugs and grounds to the control and power boards; if the wiring checks out, the pro will run resistance and voltage checks and, if needed, replace the affected board and update software where applicable. That’s safer than DIY—those components sit next to high voltage, heat, and sharp metal, and static discharge alone can finish off a $300 control.

A few tips to avoid a repeat:

keep the oven on a dedicated, properly sized circuit; don’t run repeated quick on/off cycles after an outage; and make sure the cabinet has the ventilation clearances Bosch calls for so the electronics don’t cook themselves in summer heat. If your oven is under warranty, note the code, model number, and when it appears, and share that with support—it speeds up diagnosis.

E305 is a communication error between the oven’s boards. Try a full power reset first. If it comes back, it’s likely a wiring or control-board issue that needs professional Bosch service to inspect, secure connections, and, if necessary, replace the faulty module so your oven runs flawlessly again.