Code
B1294
FIAT
B — Body
Battery supply relay circuit short to positive
AI status
Completed
Completed
100%
Causes
- Damaged wiring harness with insulation abrasion contacting B+
- Shorted or welded relay contacts inside the battery supply relay
- Faulty relay socket or connector with pin damage or corrosion
- Aftermarket accessory or improper repair tied into constant B+
- Blown or incorrect fuse allowing unintended feed paths
- Body control module (BCM) or relay driver transistor internal fault
Symptoms
- Battery-related warning lamp(s) or instrument cluster errors
- Constant battery drain or discharged battery after parking
- Certain modules remain powered when ignition off
- Intermittent or no-start conditions if fusing or control is affected
- Blown fuses related to main power circuits
- Multiple communication errors from modules on CAN bus
What to check
- Use a diagnostic scanner to read freeze-frame data and confirm B1294 is current or historic
- Visually inspect fuse box, relay, and surrounding wiring for heat damage, melted insulation or corrosion
- Measure battery resting voltage (should be ~12.4–12.8 V) and key-on voltage (~13.5–14.5 V when running)
- Check for parasitic drain with a multimeter in series at the battery (typical draw
- Inspect relay socket pins for continuity to B+ and to control output; wiggle test while observing symptoms
- Disconnect accessories or recent installs to see if code clears or drain stops
Signal parameters
- Battery voltage at constant B+: ~12.4–12.8 V (engine off)
- Key-on/run supply to relay when energized: ~12–14 V
- Relay coil/control circuit: toggles between ~0 V (off) and ~12 V (on) relative to chassis ground
- Relay coil resistance (typical): ~50–200 ohms depending on relay design — consult OEM spec if available
- Parasitic current (vehicle off, doors closed): normally
Diagnostic algorithm
- Confirm code and related B/C/U codes with a scan tool; note freeze-frame and current battery voltage.
- Visually inspect the battery area, relay/fuse box, and harnesses for melted insulation, pin corrosion, or aftermarket connections.
- With ignition OFF, measure parasitic current at the battery. If high, begin isolating loads by removing fuses/relays one at a time to identify source.
- Identify the battery supply relay and inspect connector. Unplug relay and check if the fault or parasitic draw disappears. Replace relay if fault clears.
- With relay removed, use an ohmmeter to check for continuity between the relay control/supply terminals and B+. A short to B+ will show near zero ohms where it should not.
- Trace wiring from relay to BCM/fuse box looking for chafed areas, pinched sections, or aftermarket splices. Repair damaged wiring (cut out, solder, heat-shrink or use OEM-style splices).
- If wiring and relay appear good, check BCM/relay driver output voltages with a scope or DVOM while commanding relay on/off from scan tool. Replace BCM only after confirming external wiring is intact and driver is faulty.
- After repairs, clear codes, reconnect battery, verify correct operation (no parasitic drain, relay behaves correctly) and perform a short road test or system exercise. Re-scan to confirm code does not return.
- Safety note: When working near battery/fuse boxes, disconnect negative battery terminal before major repairs and use insulated tools when probing live circuits.
Likely causes
- Shorted wiring where harness rubs on chassis or engine components
- Relay stuck welded closed or internal short in relay coil to B+
- Corroded/loose connector at relay or fuse box
- Aftermarket accessory hard-wired to battery positive
Fault status
Status
Battery supply relay circuit short to positive — unintended short to B+ detected on the relay/supply circuit; may cause modules to remain powered, blown fuses, or parasitic battery drain.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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