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Diagnostic knowledge / U300D — Ignition input signal, ON/start position - malfunction
U300D

Ignition input signal, ON/start position - malfunction

U300D is described as “Ignition input signal, ON/start position - malfunction” in the Generic OBD2 reference.

Some scan tools (for example GM and Ford dealer tools) display this code with a failure-type suffix, such as U300D-00 or U300D:00; the base code U300D is the same.

Generic OBD2

Generic OBD2: U300D

en

Ignition input signal, ON/start position - malfunction

Reference namespace
obd2
Source revision
legacy-2.2.20

Generic OBD2 definition; confirm the protocol and vehicle-specific service information.

What should I check before using this definition?

Keep the full code, module, status and freeze-frame data. Confirm the vehicle’s make, model, year and current manufacturer service information before choosing a repair. This entry does not identify a failed part by itself.

Organize a scan report or recording
Source and applicability

OBD Lens production library legacy-owner-2026-11-02-v84-evidence. This is a scoped technical reference, not a scan of your car. A catalog relationship does not certify that every ECU, year or engine returns the same signal or code definition.

Read the reference method

What does U300D mean?

Ignition input signal, ON/start position - malfunction. 1 reference families define this identifier: Generic OBD2.

Is U300D a generic or manufacturer-specific code?

Check the reference scope shown above for this identifier.

Can U300D tell me which part has failed?

This entry does not identify a failed part by itself. Confirm the vehicle’s make, model, year and current manufacturer service information before choosing a repair.

OBD Lens reference library · catalog legacy-owner-2026-11-02-v84-evidence. Sources and scope