Battery Saver Relay Circuit Malfunction
The B1838 code indicates an electrical fault in the battery saver power relay circuit. This relay is designed to automatically cut power to secondary electrical accessories—such as the radio, interior lights, and convenience modules—after a preset time when the vehicle is off, preventing deep battery discharge. When this code sets, the control module has detected an open circuit, short circuit, or relay failure that prevents normal operation.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or stuck battery saver relay
- Short to ground or voltage in the relay circuit wiring
- Corroded electrical connections or loose terminals at the relay or module
- Damaged or internally faulty body control module (BCM)
- Blown fuse in the battery saver circuit
3. Symptoms You Will Notice
- Battery drains overnight or after short periods
- Accessories like radio or interior lights stay on with ignition off
- No dome lights or delayed accessory shutdown
- Check Engine or Service light may illuminate
4. Step-by-Step Diagnosis
Scan for codes and verify B1838 is present
Inspect the battery saver relay and its fuse; replace if blown or faulty
Check for voltage, ground, and continuity at the relay socket
Inspect wiring and connectors for corrosion, damage, or loose terminals
Test the body control module (BCM) for proper operation; replace if necessary
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, but the battery may drain if accessories don't shut off. It's best to address the issue promptly to avoid a dead battery.
How much does it cost to fix?▼
Typically $100–$300, depending on whether it's a relay ($20–$50), wiring repair ($50–$150), or BCM replacement ($200–$500).