B0078 DTC – Third Row Center Seat Belt Pretensioner Circuit Fault

DTC B0078 indicates that the Supplemental Restraint System (SRS) has detected a malfunction in the third-row center seat belt pretensioner circuit. The pretensioner tightens the seat belt during a collision to help protect the occupant.

Symptoms

• Airbag (SRS) warning light ON.
• B0078 stored in the SRS module.
• Seat belt pretensioner disabled.
• Reduced restraint system performance.

Possible Causes

• Faulty third-row center seat belt pretensioner.
• Loose or damaged connector.
• Open circuit in the wiring harness.
• Short to ground or battery voltage.
• Corroded connector terminals.
• Internal SRS module fault (rare).

Typical Wiring Diagram

┌────────────────────────┐
│      SRS MODULE        │
└───────────┬────────────┘
            │
            │ Deployment Signal
            │
┌───────────▼────────────┐
│       CONNECTOR        │
└───────────┬────────────┘
            │
            │ Wiring Harness
            │
┌───────────▼────────────┐
│ Third Row Center       │
│ Seat Belt              │
│ Pretensioner           │
└────────────────────────┘

Diagnostic Procedure

1. Scan the SRS system and record all diagnostic trouble codes.
2. Inspect the pretensioner connector for bent pins, corrosion, or poor terminal contact.
3. Inspect the wiring harness for open circuits, shorts, or damaged insulation.
4. Check circuit continuity according to the manufacturer's wiring diagram.
5. Repair the fault, clear the DTC, and verify the repair with a road test and system scan.

Live Data Inspection

• Pretensioner Status: Normal
• Deployment Circuit: Active
• Open Circuit: No
• Short to Ground: No
• Short to Battery: No
• Resistance: Within manufacturer specification

Safety Notice

Disconnect the negative battery terminal and wait at least 10 minutes before servicing SRS components. Never measure or apply voltage directly to a seat belt pretensioner unless specified by the manufacturer.

Related DTCs

• B0076
• B0077
• B0079
• B0080