OBD-II code · Network (extended)
U3004 Accessory Power Relay
Fault on the accessory power relay that switches power to comfort/accessory loads (radio, infotainment, etc.) when the key is in ACC position.
Is it safe to drive with U3004?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyRelay contacts failed or coil open
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Usually unaffected
- Parts involved
- Accessory Power Relay, Relay Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.