What Does B1315 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal voltage condition in the battery saver relay coil circuit, specifically a short to battery voltage. The battery saver relay is designed to disconnect non-essential electrical loads after a predetermined time when the ignition is off to prevent battery drain. The BCM has detected that the relay coil circuit has continuous battery voltage present when it should be controllable or grounded.
Common Causes
40%
Damaged or chafed wiring harness causing the relay coil control wire to short to a battery voltage source
30%
Failed battery saver relay with internal short circuit between coil terminals or coil-to-power short
20%
Corroded or damaged connector terminals at the relay or BCM causing cross-circuit contamination
10%
Failed Body Control Module with internal driver circuit failure causing incorrect voltage output
Diagnostic Steps
1
Step 1: Perform visual inspection of the battery saver relay location, wiring harness, and all connectors for obvious damage, melted insulation, corrosion, or pinched wires. Pay special attention to areas where harnesses pass through firewalls or near sharp edges.
2
Step 2: Disconnect the battery saver relay and use a digital multimeter to measure resistance across the relay coil terminals (typically 70-120 ohms for normal relay). If open or shorted, replace relay. If within spec, measure voltage at the relay coil control wire connector terminal with ignition on - should read 0V or near ground when BCM is commanding relay off.
3
Step 3: With relay still disconnected and ignition off, check for unwanted battery voltage on the BCM control wire side of the relay connector using a multimeter. Reading should be 0V. If battery voltage is present, trace the control wire from relay to BCM for shorts to power sources.
4
Step 4: Disconnect BCM connector and inspect all terminals for corrosion, damage, or pushed-back pins. Measure resistance between the relay coil control circuit pin at BCM connector and known battery voltage sources - should read infinite resistance. If continuity exists, repair short in harness.
5
Step 5: If all wiring tests pass, reconnect all components and monitor live data for relay command status versus actual relay state. If BCM commands relay off but voltage remains high, replace BCM. Clear codes and perform functional test of battery saver system by leaving vehicle with ignition off for programmed timeout period.
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal voltage condition in the battery saver relay coil circuit, specifically a short to battery voltage. The battery saver relay is designed to disconnect non-essential electrical loads after a predetermined time when the ignition...
The most common cause of B1315 (Battery Saver Relay Coil Circuit Short To Battery) is: Damaged or chafed wiring harness causing the relay coil control wire to short to a battery voltage source
Typical repair costs for B1315 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is generally safe to drive, but the battery saver function will not operate properly, potentially leading to dead battery conditions if accessories are left on or parasitic draw exists. Repair within a few days to prevent battery discharge issues and possible electrical component damage from continuous power.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1315 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
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