U3004 — Accessory power relay

Generic OBD2

Generic OBD2: U3004

Accessory power relay

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 U3004 mean?

Accessory power relay. 1 reference families define this identifier: Generic OBD2.

Is U3004 a generic or manufacturer-specific code?

Check the reference scope shown above for this identifier.

Can U3004 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.