B1315: Battery Saver Relay Control Circuit High Voltage
The Body Control Module (BCM/GEM) has detected a short to battery voltage (high voltage) in the control circuit of the battery saver relay. This relay manages power to non-essential accessories to prevent battery drain when the vehicle is off. A short to positive in the control wire prevents the module from properly de-energizing the relay, leading to parasitic battery drain or accessory malfunction.
1. Commonly Affected Makes
2. Most Common Causes
- Battery saver relay with internally shorted coil
- Control circuit wiring (between BCM/GEM and relay) shorted to battery positive (B+)
- Failed output driver inside the BCM/GEM module
- Corroded connectors or damaged terminals in the fuse/relay box (BJB)
3. Symptoms You Will Notice
- Battery drains overnight or after short periods of inactivity
- Accessories (e.g., interior lights, radio) remain on after ignition is off
- Check Engine Light or BCM-related warning light illuminated
4. Step-by-Step Diagnosis
Scan for B1315 and any related BCM codes
Inspect battery saver relay for signs of damage or internal short; test relay coil resistance
Check control circuit wiring from BCM to relay for shorts to battery positive using a multimeter
Inspect connectors at BCM and relay box for corrosion, bent pins, or loose terminals
If wiring and relay are good, suspect a failed BCM output driver; perform BCM output test if available
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, but the battery may drain, leaving you stranded. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
Typically $100-$300 for relay and wiring repairs; up to $800+ if BCM replacement is needed.