How to Fix the Bosch Oven E305 Error Code

Is your Bosch oven flashing the E305 error code and not responding like it should? We’ll break down what the E305 error really means and walk you through how to troubleshoot and fix it yourself.

If you find out that you need any replacement parts for your appliance while you’re troubleshooting, you can enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

The information in this article may not apply to your specific appliance model. We recommend consulting your manufacturer’s documentation or contact us with any questions.

What does the error code mean?

On Bosch 800 series slide-in gas ranges, the E305 error message on the front control panel indicates a communication issue between two specific components:

• The touch control module (TCM) – This is the interface board behind the glass touchscreen. It monitors the touch pads and communicates with the control module.
• The control module – This is the main controller board that regulates oven functions. It communicates with the TCM and other range components.

Specifically, the E305 code means communication is lost between these two boards. It could also mean communication is lost between the TCM and the user interface display.

When this error occurs, the touchscreen and display will be unresponsive. The oven won’t heat up and no cooking functions will operate. A reset is required to restore functionality.

The problem stems from a wiring or component fault rather than a software issue. So the solution involves checking connections, wires and ultimately replacing a faulty main control board.

Safety precautions

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind: 

• Always power off and unplug your appliance or switch off the circuit breaker before attempting any maintenance or replacement work. This keeps you safe by preventing any risk of injury from electric shock.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with bare wet hands. Make sure the work area is completely dry.
• Check your user manual to see if there are specific installation or safety instructions for your part or appliance. 
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• If the appliance has recently been used, give it plenty of time for any heating parts to cool down before working on it. 
• Take pictures or make a note of wiring terminals or other connections before disconnecting to prevent any problems with reassembly.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.

Troubleshooting steps 

Step 1 – Inspect wiring harnesses and connections

The first troubleshooting step is to thoroughly inspect the wiring between the TCM and the control module. Here’s how:

1. Remove power from the appliance.
2. Access the back of the range by pulling it out from the wall. Remove any access panels if needed.
3. Locate the ribbon cable or wiring harness between the TCM and the control module. The TCM is housed behind the touchscreen glass.
4. Inspect the length of the cable for any cuts, pinches, or damage. Electrical tape or fraying are signs of damage.
5. Check where the cable plugs into the TCM and control module. Make sure connections are tight within the normal operating range and contain no bent pins.
6. Check ground wires and power supply lines as well.

Faulty wiring and broken wires are the most common reason for an E305 error. Before replacing components, double-check that cables are undamaged and seated properly. If damage is found, the wires will need replacement.

Step 2 – Check voltage at the control module

If the wiring checks out okay, the next step is verifying power to the control module. Here’s how to test:

1. Unplug the range and access the rear control board panel.
2. Use a multimeter to check the pins on the module’s connection block or power supply board. Refer to the appliance schematic for diagrams and voltages.
3. Check for 120V incoming power from the power cord. Then check voltage readings at other pins where wires are connected.
4. If incoming 120V is present but there is no voltage at other pins, there is likely a faulty connection. Check where those wires terminate.
5. If voltages aren’t 120V as expected, there is a deeper issue like a tripped fuse or home wiring problem. Further diagnosis may be needed.

Checking pins can help narrow down if it’s a board problem or simply an incoming power supply issue. Probe the pins carefully without touching adjacent pins.

Step 3 – Verify option code settings

The control module requires the correct option code to be set for the specific appliance model. An incorrect code can prevent proper communication.

Here are the steps for checking the option code:

1. Initiate service mode by pressing a series of buttons – refer to the appliance owner’s manual.
2. When the option code screen comes up, note the 4-digit code shown. For an 800 series range, it should be 2078.
3. If incorrect, use the keypad to enter the proper code then save. Instructions should be in the user manual.
4. Exit service mode and power up the appliance fully. The E305 error on the electronic display may be resolved after setting the right option code.

The code tells the control module which specific model it’s installed in and adjusts functions accordingly. An improper code is commonly misdiagnosed as a faulty board.

Step 4 – Replace the touch control module

If the E305 error persists after the above steps, replace the TCM assembly behind the touchscreen:

1. Power down and unplug the range.
2. Remove any brackets or panels to access the glass display.
3. Disconnect the ribbon cable and grounding wires from the TCM. Remove any mounting screws.
4. Remove the glass display panel and old TCM. Transfer any brackets or hardware.
5. Install the new replacement TCM by reversing the removal steps. Make sure it’s oriented correctly.
6. Reconnect the ribbon cable and wiring. Double check everything is tight.
7. Carefully reinstall the display panel and any other hardware. Do not overtighten any screws.
8. Restore power and test for the error code. Also, check for proper touchscreen response.

Replace the entire touch control module if available. Only replace the TCM board itself if necessary. Take photos while disassembling to help with reassembly.

Step 5 – Replace the control module

If the problem persists after a new TCM module, the last resort is replacing the oven’s control module:

1. Turn off power and gas lines. Disconnect all wiring harnesses.
2. Remove mounting screws to free the control module from the chassis.
3. Install the replacement part and fasten it securely with the original screws.
4. Reconnect each wiring harness to the proper terminal. Refer to the wiring diagram.
5. Review your work to make sure there is no loose connection in the wiring and that everything is correctly oriented and tightened.
6. Restore power and gas lines and clear any leftover error codes until the new control module initializes.
7. Carry out appliance functionality tests. If the E305 is resolved, the control module was faulty.

Only replace the control module if sure it’s a board issue. Have the prior TCM repair steps completed first before ordering a new control module.

Additional information

Thank you for reading! We hope you found this information useful to get your oven working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our thousands of free videos and troubleshooting guides available. If you need replacement parts or some extra help, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, order parts, read our DIY blog, and more.

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