enbgde
B1878 Manufacturer-specific Basic entry

Seatbelt Driver Pretensioner Circuit Short to Battery

Updated 2026-10-10 · Body (manufacturer-specific)

Severity
High
Typical repair cost
40 – 350 EUR
System
Body

This is a manufacturer-specific code. Its exact meaning can differ between makes; the definition below follows the most common usage.

What it means

B1878 is stored when the body control module measures a voltage in the Seatbelt Driver Pretensioner circuit above the expected maximum, typically because the signal wire is shorted to battery voltage or the circuit is open and pulled up internally.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

Advertisement728 × 90

Symptoms

  • The affected function (lighting, locking, windows, seats, climate or restraint) does not work or works intermittently
  • Warning light or message on the instrument cluster
  • Possible battery drain if a module stays awake

Common causes

  1. Damaged, chafed or corroded wiring in the Seatbelt Driver Pretensioner circuit
  2. Corroded, loose or water-damaged connector terminals
  3. Failed Seatbelt Driver Pretensioner component (sensor, solenoid or actuator)
  4. Poor ground connection for the module or component
  5. Faulty control module driver (rare, confirm all else first)

How to diagnose

  1. Read freeze frame data and note when the code set (cold start, under load, after rain)
  2. Inspect the Seatbelt Driver Pretensioner connector for bent pins, corrosion and water; wiggle the harness with the engine running and watch live data
  3. Measure supply voltage and ground at the connector with the key on
  4. Check the signal wire for shorts to ground or battery and for continuity to the control module
  5. Test or substitute the Seatbelt Driver Pretensioner only after wiring and connectors are confirmed good
  6. Clear the code and complete a drive cycle to confirm the repair

Frequently asked questions

Can I keep driving with B1878?

Not for long. This code can lead to expensive follow-up damage or affects safety systems; have it checked as soon as possible.

Will clearing B1878 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

B1876B1877B1879

Nearby codes in this group