B1315

Battery Saver Relay Coil Circuit Short To Battery

Body Chassis/Safety Battery Management 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The battery saver relay coil has an unwanted direct connection to battery voltage, causing it to stay energized when it shouldn't. Think of it like a light switch that's permanently wired to power instead of being controlled—it can't turn off properly.

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Symptoms You May Notice

3 known symptoms for this code
Battery drains rapidly when vehicle is parked
Electrical components remain powered when engine is off
Check Engine Light or warning indicator illuminated
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the battery saver relay coil circuit voltage and ground continuity. It expects the coil to be de-energized at rest with minimal current draw. When the coil shorts directly to battery voltage, the ECU detects abnormal voltage presence on the control circuit when it should be inactive.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Relay Coil Control Voltage 0V (de-energized) or commanded voltage only Battery voltage present when coil should be off
Parasitic Current Draw Less than 50mA at rest Greater than 500mA sustained drain
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Wiring inspection and repair
Check the battery saver relay connector and wiring harness for damaged insulation, corrosion, or exposed wires shorting to battery positive.
2
Battery saver relay replacement
Replace the relay if internal winding is shorted; disconnect negative battery terminal first, then swap the relay in its designated socket.
3
Ground connection cleaning
Clean and re-secure all ground connections to the relay module and ECU to eliminate high-resistance faults causing false shorts.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1315 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code B1315

What happens after you fix the fault

Once the fault is repaired, B1315 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.