What Does U3004 Mean?
DTC U3004 indicates that a control module has detected a malfunction with the Accessory Power Relay circuit. The accessory power relay provides switched 12V power to vehicle accessories (radio, power windows, power seats, etc.) when the ignition is in the accessory or run position. This code is set when the relay output does not match the expected state based on the ignition switch position or BCM command.
Common Causes
35%
Failed accessory power relay stuck open or stuck closed, not responding to BCM control signals
25%
Open or shorted wiring in the relay control circuit between the BCM and the accessory relay
20%
Body Control Module relay driver circuit failure — unable to command the accessory relay properly
20%
Blown fuse in the accessory relay power feed or relay coil supply circuit
Diagnostic Steps
1
Step 1: Locate the accessory power relay in the fuse/relay box — swap it with an identical relay from a non-critical circuit (e.g., horn relay) and check if the condition follows the relay or stays in the original location.
2
Step 2: With the relay removed, use a multimeter to check for battery voltage on the relay power input terminal and the relay coil supply terminal — both should show battery voltage with ignition on.
3
Step 3: Check the relay control signal from the BCM — backprobe the relay coil ground control wire and verify the BCM provides ground when the ignition is in the accessory or run position (should read less than 0.5V when commanded on).
4
Step 4: Inspect the relay socket for burnt, loose, or corroded terminals — clean or replace the socket if damage is found.
5
Step 5: If the relay and wiring test good, check BCM operation — use the scan tool to command the accessory relay on/off via bi-directional controls and verify the BCM can toggle the relay.
Estimated Repair Cost
$30 - $400
Parts + labor, varies by vehicle and location
DTC U3004 indicates that a control module has detected a malfunction with the Accessory Power Relay circuit. The accessory power relay provides switched 12V power to vehicle accessories (radio, power windows, power seats, etc.) when the ignition is in the accessory or run position. This code is set ...
The most common cause of U3004 (Accessory Power Relay) is: Failed accessory power relay stuck open or stuck closed, not responding to BCM control signals
Typical repair costs for U3004 range from $30 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Generally safe to drive. Accessory relay failure may cause loss of convenience features such as radio, power windows, or power seats. If the relay is stuck on, it could cause a parasitic battery drain when the vehicle is off.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U3004 to identify the root cause.
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Quick Info
Category
Network
System
Electrical System / Accessory Power Distribution
Difficulty
Type
Generic (SAE)
Recommended Tools
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