Code
B1315
ALFA ROMEO
B — Body
Battery saver relay coil circuit short to positive
Views:
UK: 4
EN: 8
RU: 8
AI status
Completed
Completed
100%
Causes
- Short to battery positive in the relay coil supply circuit
- Damaged or shorted battery saver relay (internal coil short)
- Corroded/damaged relay connector or terminals
- Wiring harness chafed and contacting a positive conductor
- Faulty Body/BCM control module output transistor or internal short
- Water ingress or contamination in relay/connector area
Symptoms
- Battery saver relay stuck closed (accessories remain powered with ignition off)
- Parasitic battery drain or dead battery after vehicle off
- Accessories not turning off as expected (interior lights, radio, etc.)
- Related warning lights or body electrical faults
- Stored B1315 code and possible other body electrical DTCs
What to check
- Retrieve freeze frame and any related codes with a diagnostic scanner
- Visually inspect relay, connector, and wiring for damage, corrosion, or signs of water ingress
- Check condition and fuses for accessory/battery saver circuits
- Perform wiggle test on wiring harness near relay while monitoring voltage/continuity
- Disconnect relay and check circuit behavior (does problem clear?)
- Measure voltage at relay coil connector with ignition ON and OFF
Signal parameters
- Coil supply voltage (should be ~0V when not energized if driven low; may be ~12V when commanded ON)
- Coil resistance (typical automotive relay coils: ~20–200 Ω; consult vehicle spec)
- Control output voltage from BCM: 0 V (ground drive) or +12 V depending on design
- Parasitic current when relay should be off: should be low (
Diagnostic algorithm
- Connect diagnostic scanner, record B1315 and any related codes, clear code and see if it returns
- Perform visual inspection of the battery saver relay, socket, and harness for damage, corrosion, moisture, or rodent chewing
- With ignition OFF, disconnect battery saver relay. Check if parasitic drain stops (measure current at battery: should drop to normal background level)
- Measure resistance across relay coil with relay removed. If coil reads near 0 Ω (short) or open, replace relay. Compare to manufacturer spec if available
- With connector disconnected, measure voltage between coil control pin and battery positive/ground with ignition OFF and ON. A short to positive is indicated if the control circuit reads battery voltage when it should be low or open
- If control circuit is shorted to +12V with connector removed, isolate wiring: inspect harness for chafe points, unplug intermediate connectors and retest to locate short
- If wiring is good, test the BCM/BCU control output. Replace or repair module only after confirming wiring and relay are good and module is faulting the circuit
- After repair or replacement, clear codes, verify correct relay operation, and recheck for parasitic draw and code recurrence
Likely causes
- Shorted wiring between relay connector and battery positive (chafed harness)
- Failed battery saver relay with internal coil short to +12V
- Corroded connector causing bridging to positive
- Damaged BCM/BCU driver transistor providing permanent +12V to coil
Fault status
Status
Battery saver relay coil circuit shorted to battery positive. Relay may be continuously energized causing accessory power to stay on and possible battery drain.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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