U3004Accessory Power Relay
- Generic OBD-II code · Network
- How the car detects it
- U3004 concerns the relay, or electronic switch, that feeds the accessory (ACC) circuits once the car is in accessory or run mode. On GM trucks the body module reads the ignition inputs, decides the power mode and energises the matching relays itself. Mazda documents the code in the start stop unit as U3004:17, an ACC relay line above its threshold. Its bulletin SA-023-23 for the 2017–2022 CX-5 traces it to drink spilled near the front cupholder, which corrodes connector C-16: the ignition then cannot be switched off, infotainment stays on and the battery runs flat. Mazda's MT-001/21 lists the same entry among faults caused by aftermarket dongles plugged into the diagnostic connector. The stuck accessory feed matters more to the driver than the code; no MIL.
- What you may notice
- Ignition or accessory mode cannot be switched off, radio stays on
- Flat battery and no-start after the car has stood
- Accessory functions dead in accessory mode
- Likely causes
- LikelySpilled liquid corroding a connector in the relay control or feed circuit
- PossibleAftermarket device on the diagnostic socket or accessory circuit feeding back voltage
- PossibleAccessory relay sticking or its coil damaged
- RareFault in the module that drives the relay
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.