B1304: Accessory Delay Relay Coil Short to Battery
The B1304 code indicates a short to battery voltage in the accessory delay relay coil circuit. This relay supplies power to accessories like the radio, power windows, and power outlets after the ignition is turned off, allowing them to operate for a set time or until a door is opened. A short to battery means the relay coil control circuit is receiving constant battery voltage when it shouldn't, which can keep the relay permanently engaged or prevent proper control by the Body Control Module (BCM) or Generic Electronic Module (GEM) in Ford vehicles.
1. Commonly Affected Makes
2. Most Common Causes
- Internally damaged accessory delay relay with a shorted coil
- Wiring in the relay control circuit with damaged insulation contacting battery power
- Faulty BCM/GEM module that keeps the control circuit incorrectly activated
- Relay connector or harness with bent pins, corrosion, or metallic bridges
- Aftermarket electrical modifications (e.g., accessory installations) causing circuit bridges
3. Symptoms You Will Notice
- Accessories (radio, windows, power outlets) remain on continuously after ignition off
- Accessories do not operate at all
- Battery drain due to accessories not shutting off
4. Step-by-Step Diagnosis
Check for technical service bulletins (TSBs) related to B1304 for the specific vehicle
Inspect the accessory delay relay and its connector for damage, corrosion, or bent pins
Test the relay coil resistance and verify it is not shorted to battery voltage
Check the wiring between the relay and BCM/GEM for shorts to battery or ground
If wiring and relay are okay, test the BCM/GEM output to the relay control circuit
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but you may experience a dead battery if accessories stay on. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the relay, wiring, or BCM/GEM module needs replacement.