OBD2 Code B1305: Accessory Delay Relay Coil Short
The B1305 code indicates that the control module has detected a short to ground in the coil circuit of the accessory delay relay. This relay keeps comfort components like power windows, radio, and power outlets powered for a set time after the ignition is turned off, or until a door is opened. The short to ground prevents the module from properly controlling the relay, resulting in a lower than expected voltage on the monitored control line.
1. Commonly Affected Makes
2. Most Common Causes
- Internal coil of the accessory delay relay shorted to ground
- Control circuit wiring between the module and relay shorted to ground
- Damaged, wet, or corroded harness connector or pin causing ground contact
3. Symptoms You Will Notice
- Accessory delay function inoperative (power windows, radio, etc. turn off immediately when ignition is off)
- Possible blown fuse for the accessory delay relay circuit
4. Step-by-Step Diagnosis
Check for technical service bulletins (TSBs) related to B1305 for the specific vehicle
Visually inspect the accessory delay relay and its wiring for damage, corrosion, or loose connections
Test the relay coil resistance and check for continuity to ground; replace relay if shorted
If relay is good, check the control circuit wiring from the module to the relay for a short to ground
If wiring is intact, suspect a faulty control module (BCM, GEM, or FEM) and perform further diagnostics
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive. The main issue is that the accessory delay feature may not work, but the vehicle remains drivable.
How much does it cost to fix?▼
The cost can range from $50 to $200 for relay and wiring repairs, or up to $500-$1000 if the control module needs replacement.