Code
B1315
FIAT
B — Body
Battery saver relay coil circuit short to positive
Views:
UK: 3
EN: 7
RU: 8
AI status
Completed
Completed
100%
Causes
- Short to battery positive (B+) on the relay coil feed or control circuit
- Stuck or welded relay contacts allowing coil feed to backfeed
- Faulty battery saver relay (internal shorted coil)
- Damaged or chafed wiring harness contacting chassis or B+ conductor
- Faulty body control module (BCM)/power module driver
- Poor connector pin fit or corroded terminals creating unintended connection
Symptoms
- Battery saver function not operating (interior electronics may stay powered)
- Battery drain when vehicle is off
- Related warning lamps or messages on dash
- Intermittent loss of accessories or unexpected accessory power
- Possible blown fuses or repeated fuse failures for body circuits
What to check
- Check for stored freeze-frame data and related codes in BCM
- Visually inspect battery saver relay and surrounding wiring for heat damage or melted insulation
- Check connector pins for corrosion, bent pins, or pushed-out terminals
- Measure voltage at relay coil feed and control terminals with ignition off and on
- Test relay by substitution with known-good relay of same type if available
- Check for aftermarket accessories or recent work in the area that could have disturbed wiring
Signal parameters
- Nominal coil supply voltage: ~12 V (battery) when feed is powered
- Expected control/driver voltage: pulled low or switched to ground by BCM to energize (varies by vehicle)
- When relay is OFF: coil control terminal should be near 0 V or open circuit (not constant B+)
- Typical relay coil resistance (varies by relay): tens to a few hundred ohms — measure with relay removed
- Coil current when energized: typically 0.05–0.5 A depending on relay design
Diagnostic algorithm
- Retrieve freeze-frame and related codes from the BCM. Note conditions when fault set (ignition state, battery voltage).
- Perform a visual inspection: battery saver relay, fuse box, harness routing. Look for melted insulation, pinched wires, damaged relay housing, or aftermarket taps.
- With ignition OFF, disconnect the relay. Measure resistance between the coil terminals of the removed relay to ensure coil is not shorted to its housing or B+ terminal. If coil resistance is near 0 Ω, replace relay.
- Backprobe the relay socket with ignition OFF: measure voltage between coil feed terminal and ground. If battery voltage is present at the relay feed when it should be off, trace that feed back toward the fuse/relay power source for a short to B+.
- With relay removed, check for continuity from the coil control terminal to B+ (should be open). If continuity exists, isolate harness sections and unplug connectors to localize the short.
- Inspect and wiggle harness while monitoring voltage/continuity to reproduce intermittent shorts. Pay attention to harness runs near engine, hinge points, and body seams.
- If wiring and relay check OK, verify BCM driver output with a scope or DVOM while commanding relay on/off from scan tool. If driver output is stuck high, suspect BCM or power module; confirm against wiring diagrams and test other BCM outputs.
- If BCM driver is faulty, confirm with manufacturer diagnostics before replacing. Repair any damaged wiring, connectors, or replace relay as required, then clear codes and retest under the same conditions.
Likely causes
- Shorted relay coil inside battery saver relay
- Pinched or melted insulation on coil feed causing contact with B+
- Connector pushed into wrong position or corrosion bridging pins
- Aftermarket accessory tied into constant battery supply near relay harness
Fault status
Status
Battery saver relay coil circuit short to positive — control module detected battery voltage present on relay coil/control circuit when it should be inactive. Possible wiring short, relay failure, or module driver fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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