U3004: Accessory Power Relay
Methodology: We combine code standards with complaint and reliability patterns, then review for clear, vehicle-first diagnosis steps.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What Does U3004 Mean?
U3004 is a diagnostic trouble code indicating: Accessory Power Relay. This code relates to the vehicle systems system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
Symptoms of U3004
- ⚠️ Check Engine Light (MIL) illuminated
- ⚠️ Accessory Power Relay not functioning as expected
- ⚠️ Related system may be in fail-safe mode
- ⚠️ System warning light illuminated
Common Causes
- 🔍 Faulty Accessory Power Relay
- 🔍 Wiring or connector issue in Accessory Power Relay circuit
- 🔍 Related mechanical or electrical fault
- 🔍 ECM/PCM issue (rare)
Frequently Asked Questions
What does U3004 mean?
Can I drive with code U3004?
How much does it cost to fix U3004?
What To Do Next
Possible Fixes
- 🔧 Inspect Accessory Power Relay and related wiring
- 🔧 Replace faulty Accessory Power Relay
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1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.