Bosch Dryer Error Code E:9002

Error code E:9002 on a Bosch dryer indicates a power supply fault, specifically that the control board cannot complete its security test of the fused relay contacts because the incoming mains voltage is too low. This self-test is a built-in safety routine the dryer performs to verify that critical relay contacts are functioning correctly before allowing a cycle to begin. When mains voltage drops below the minimum threshold required to execute this test, the dryer halts operation and displays E:9002 rather than risk running with an unverified relay state. This code is the 4-digit equivalent of the older E:89 code found on some Bosch models.

The fused relay contact test is a protective measure designed to confirm the relay is opening and closing as expected. If mains voltage is insufficient, the control board cannot generate reliable test conditions, so the diagnostic is aborted entirely. The root cause in most cases is not a failed component inside the dryer itself, but rather a problem with the household electrical supply, such as a brownout, a shared circuit under heavy load, an undersized or failing breaker, or loose wiring connections at the outlet, junction box, or service panel.

Because the first diagnostic step is to check the customer's mains voltage, technicians should use a multimeter to measure voltage at the dryer's outlet before opening the unit. If voltage is within the specified range and the error persists, the power inlet components, wiring harness, or control board may warrant further inspection. Intermittent low-voltage events, sometimes caused by utility grid issues or peak demand periods, can also trigger this code unpredictably.