mypros+
Error code reference

Bosch Dryer Error Code E:0103

Power Unit / Safety test

Bosch codesBosch dryer codes

Power Unit / Safety test - security test of fused relay contacts failed (test via master relays) (Error) (4-digit equivalent of E:90).

First step from the service manual

Check wire harness between Power Unit and motor.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for E:0103.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What E:0103 means on a Bosch dryer

Error code E:0103 on a Bosch dryer indicates a failure in the Power Unit's internal safety test, specifically the security test of the fused relay contacts as verified through the master relays. This is the 4-digit equivalent of the simpler E:90 code. The Power Unit contains relays that control motor operation, and the control board performs an automated self-test to confirm these relay contacts open and close correctly. When the contacts of a fused or welded relay fail to respond as expected during this test cycle, the E:0103 fault is logged and the dryer halts operation to prevent unsafe conditions.

The most likely point of failure is in the wire harness connecting the Power Unit to the motor. A damaged, corroded, or improperly seated connector in this harness can cause the master relay test to register incorrect feedback, triggering the fault even when the relay hardware itself is functional. Intermittent connection problems are particularly common in this harness because the dryer's vibration and heat cycles can loosen terminals over time.

If the harness checks out and continuity is confirmed at all pins, the fault may indicate an actual relay contact failure within the Power Unit itself. Relay contacts can weld together or fail to make proper contact due to age, electrical arcing from motor load spikes, or contamination. In this case, the Power Unit assembly would require replacement, as the relays are typically integrated into the unit and not serviceable individually.

Source: manufacturer service documentation.

Common causes of E:0103

  1. 01

    Faulty or damaged wire harness between Power Unit and motor

    Wiring / connection

    A broken, corroded, or loose connector in the harness between the Power Unit and the motor can cause the relay self-test to fail even if the relay itself is intact. Inspect all pins and connectors along this harness for damage, oxidation, or improper seating.

  2. 02

    Fused or welded relay contacts in the Power Unit

    Part replacement

    Relay contacts inside the Power Unit can weld together or fail to make proper contact due to electrical arcing or normal wear over time. If the harness tests good, the Power Unit itself is likely the faulty component.

  3. 03

    Failed Power Unit assembly

    Part replacement

    If both the harness and individual relay contacts have been ruled out, the Power Unit as a whole may have an internal electronic failure affecting the relay control circuitry. Replacement of the Power Unit assembly would be required.

  4. 04

    Loose or corroded connector at the motor

    Wiring / connection

    The motor-side connector in the harness is subject to heat and vibration, which can cause terminal loosening or corrosion. Check the connector at the motor plug specifically for bent pins or oxidized contacts.

See the test procedure for each cause

Frequently asked questions about E:0103

What does E:0103 mean on a Bosch dryer?
E:0103 is a Power Unit safety test failure code, specifically indicating that the security test of the fused relay contacts failed when tested through the master relays. It is the 4-digit version of the E:90 code. The dryer performs this self-test to confirm that the motor control relays are operating safely, and it stops running when the test does not pass.
How do I fix the E:0103 error on my Bosch dryer?
Start by inspecting the wire harness between the Power Unit and the motor for any signs of damage, loose connectors, or corrosion. Reseat all connectors and check for continuity across the harness. If the harness is in good condition, the Power Unit assembly likely has a failed relay and will need to be replaced by a qualified technician.
Is it safe to use my Bosch dryer with an E:0103 error?
No, you should not continue operating the dryer while this error is active. The E:0103 code indicates a failure in a safety relay test that is designed to protect the dryer and your home. The dryer disables itself for this reason, and running it in a faulted state is not recommended until the underlying cause is diagnosed and repaired.
Will resetting my Bosch dryer clear the E:0103 error?
A reset may temporarily clear the code, but because E:0103 is triggered by an active hardware safety test failure, the error will almost certainly return as soon as the dryer performs its self-test again. The underlying issue with the harness or the Power Unit relay must be physically repaired before the code will stay cleared.
How much does it cost to repair a Bosch dryer with an E:0103 error?
Repair costs vary depending on what component is at fault. If the fix involves reseating or replacing the wire harness, costs are generally lower, typically in the range of $75 to $200 including labor. If the Power Unit assembly requires replacement, parts and labor combined can range from $200 to $450 or more depending on your location and the specific model.

Related Bosch dryer codes

All Bosch dryer codes
View all 94 Bosch dryer codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass