B1256
Low Severity (Level 2)Air Temperature External Sensor Circuit Short To Battery
B1256 usually means air Temperature External Sensor Circuit Short To Battery.
Can you still drive with B1256?
⚠️Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
Typical repair cost: $120 – $600
Severity Level 2 — Low
This code indicates a minor issue that is unlikely to cause immediate driveability problems. You can typically continue driving but should have the vehicle inspected at your earliest convenience.
Common Symptoms
- Electrical system staying on or functioning when they shouldn't (powered continuously)
- Battery draining overnight or when vehicle is parked
- Electrical system not responding to controls — stuck in one state
- Excessive current draw on the battery voltage/system voltage circuit (fuse may blow repeatedly)
Possible Causes
- Damaged wiring in the battery voltage/system voltage harness shorted to a 12V power source — wiring insulation chafed through from rubbing against metal body panels
- Water intrusion or corrosion in battery voltage/system voltage electrical connector causing internal short to battery voltage
- Failed battery — internal short to power within the component
- Aftermarket accessory installation tapped into the wrong circuit, back-feeding 12V
Common Fixes
- Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($10-111 at shop, free at auto parts store for basic scan)
- Visually inspect the battery voltage/system voltage wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $67 diagnostic fee at shop)
- Repair or replace damaged section of wiring harness where short is located — solder and heat-shrink all connections, don't use crimp connectors on critical circuits ($104-382 depending on accessibility)
- If battery is internally shorted, replace with a quality OEM or OEM-equivalent aftermarket unit ($100-500)
- Clean all ground points related to the battery voltage/system voltage — remove bolt, sand contact surface to bare metal, apply dielectric grease, and torque to spec ($38-125 at shop)
Estimated Repair Cost
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
Frequently Asked Questions
What does B1256 mean?
B1256 stands for "Air Temperature External Sensor Circuit Short To Battery". B1256 usually means air Temperature External Sensor Circuit Short To Battery.
Can you drive with B1256?
Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
How much does it cost to fix B1256?
Repair costs for B1256 typically range from $120 to $600, depending on your vehicle make, model, and local labor rates. Common fixes include: Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($10-111 at shop, free at auto parts store for basic scan); Visually inspect the battery voltage/system voltage wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $67 diagnostic fee at shop); Repair or replace damaged section of wiring harness where short is located — solder and heat-shrink all connections, don't use crimp connectors on critical circuits ($104-382 depending on accessibility).
Will B1256 clear itself?
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