U3004 — Accessory Power Relay

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?

U3004 indicates: Accessory Power Relay. The vehicle's computer has detected that the Accessory Power Relay is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code U3004?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with U3004 for extended periods may cause additional problems.

How much does it cost to fix U3004?

Repair costs for U3004 typically range from $80 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect Accessory Power Relay and related wiring
🔧 Replace faulty Accessory Power Relay

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

U3004: Accessory Power Relay