B1878: Seatbelt Driver Pretensioner Circuit Short to Battery
What does B1878 mean?
B1878 is a diagnostic trouble code indicating "Seatbelt Driver Pretensioner Circuit Short to Battery". The ECU is detecting a voltage reading that is below the expected range in the seats circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.
Symptoms you may notice
- Check engine light (MIL) illuminated on dashboard
- Intermittent warning lights
- Erratic gauge readings
Estimated repair cost
Typical range in Australia (parts + labour)
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed seats sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
This code sits in the occupant restraint system. The airbags or pretensioners may not fire in a crash, and on some faults they can fire when they should not. The car will usually drive and feel completely normal, which is exactly why this one gets ignored. Have it diagnosed before you carry passengers, and do not clear the code to make the light go away.
Get a diagnosis for YOUR car
Code B1878 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.