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Diagnostic knowledge / U300F — Ignition input signal, accessory position - malfunction
U300F

Ignition input signal, accessory position - malfunction

U300F is described as “Ignition input signal, accessory 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 U300F-00 or U300F:00; the base code U300F is the same.

Generic OBD2

Generic OBD2: U300F

en

Ignition input signal, accessory 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 U300F mean?

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

Is U300F a generic or manufacturer-specific code?

Check the reference scope shown above for this identifier.

Can U300F 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