Bosch Washer F28 Error Code - Causes & Fix

Bosch Washer F28 Error Code — What It Means

The F28 error code (sometimes displayed as E28) indicates a flow sensor fault on your Bosch washing machine. The control board is not receiving a valid signal from the flow sensor, so the machine cannot confirm that water is entering at the correct rate. Bosch’s official documentation identifies this code specifically as a flow sensor issue, not a drain problem. The sensor monitors incoming water flow during the fill cycle. When the sensor circuit fails, is disconnected, or reports flow that doesn’t match what the control expects, the machine stops and displays F28. This can happen because of an actual sensor or wiring failure, or because restricted water supply prevents normal flow and the sensor correctly reports the problem.

Jump to Fix

Common Causes

• Faulty flow sensor The flow sensor itself has failed internally or its reed switch or Hall-effect element no longer generates a proper signal when water passes through.
• Loose or corroded sensor connector The wiring harness plug at the flow sensor has worked loose, gotten wet, or developed corrosion that interrupts the signal path to the control board.
• Kinked or restricted inlet hoses Supply hoses are bent, pinched behind the washer, or internally restricted so that actual water flow is too low for the sensor to register correctly.
• Closed or partially closed supply valves One or both hot and cold shut-off valves at the wall are not turned fully open, limiting flow enough to trigger a sensor fault.
• Clogged inlet screens Fine mesh filters inside the hose couplings at the back of the washer are packed with sediment or mineral buildup, choking flow before it reaches the sensor.
• Control board misreading the sensor The main PCB has a fault in the sensor input circuit and interprets a valid signal as an error, though this is less common than sensor-side problems.

Step-by-Step Fix

1. Unplug the washer and turn off both hot and cold supply valves at the wall to make the work area safe.
2. Check both supply valves are turned fully counterclockwise to the open position, then inspect the inlet hoses for kinks, sharp bends, or crushing where they connect or run behind the cabinet.
3. Remove both inlet hoses from the back of the washer, pull out the fine mesh screens from each inlet port with needle-nose pliers, and rinse them under running water to clear any sediment or scale.
4. Locate the flow sensor on the inlet water path inside the washer (you may need to remove the top or rear panel depending on your model), then unplug its connector and inspect the terminals and pins for moisture, green corrosion, or looseness.
5. Reconnect the sensor firmly, reassemble any panels you removed, reattach the inlet hoses, turn on the water supply, and plug in the washer to test whether the code clears.
6. If F28 persists, consult your model’s service manual for flow-sensor test procedures (resistance or signal checks) or arrange service, because Bosch states this fault cannot be cleared without component-level repair or replacement.
7. After successful repair, run a short rinse or test cycle to confirm normal fill behavior and verify the error does not return.

Parts Often Needed

When to Call a Pro

Call a qualified appliance technician if you’ve verified full water supply, cleaned the inlet screens, reseated the flow-sensor connector, and the F28 code still appears. Testing the sensor circuit requires a multimeter and your model’s specifications, and the sensor itself is often buried behind panels or the inlet manifold. Bosch’s own guidance states this fault cannot be rectified by the user and recommends arranging service. If you are uncomfortable working with live water connections, partially disassembling the cabinet, or interpreting wiring diagrams, professional diagnosis will quickly isolate whether the sensor, harness, or control board is at fault and make sure the correct part is replaced the first time.