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DTC codes / B00xx · Airbags, seats, doors, lights and comfort systems / B0078

B0078Third Row Right Seat Belt Pretensioner Deployment Control

B0078 indicates that the restraint control module has detected a fault in the deployment circuit for the third-row right seat belt pretensioner, which is the device that retracts the belt in a crash. The module monitors the circuit's resistance and continuity, and it sets this code when the signal falls outside the expected range or the deployment command cannot be verified.

SystemBody
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

  • The supplemental restraint system (SRS) warning light stays illuminated on the dashboard.
  • A chime or message may appear indicating a restraint system fault.
  • The third-row right seat belt may not retract or lock as it should during a sudden stop.
  • In some vehicles, the pretensioner may deploy unexpectedly or not at all in a collision.
  • Often no symptoms besides the warning light, with the belt feeling normal in everyday use.

Common causes, most likely first

  1. A damaged or disconnected electrical connector at the third-row right pretensioner.
  2. Corroded or frayed wiring in the seat belt pretensioner circuit, often from seat movement or cargo loading.
  3. A failed pretensioner squib or deployment element inside the seat belt assembly.
  4. A fault within the restraint control module itself, though this is less common.
  5. Water intrusion or physical damage to the harness running to the third-row seat area.
  6. An open or shorted circuit caused by a previous collision repair or aftermarket accessory installation.

How to diagnose and fix it

  1. Inspect the third-row right seat belt pretensioner connector for looseness, corrosion, or damage and reseat it firmly.
  2. Check the wiring harness along the seat and cargo area for pinches, chafing, or breaks, repairing as needed.
  3. Measure the resistance of the pretensioner circuit with a digital multimeter and compare it to the manufacturer's specification.
  4. If resistance is out of range, isolate the pretensioner from the harness to determine whether the fault is in the squib or the wiring.
  5. Replace the third-row right seat belt pretensioner assembly if the squib is open or shorted.
  6. Clear the diagnostic trouble codes and verify the SRS light goes out and stays off after a test drive.
  7. If the code persists after circuit repairs, follow the manufacturer's diagnostic flow to test the restraint control module.

Before you replace the pretensioner

  • A loose connector under the third-row seat is the most common cause of B0078, especially after cargo has been loaded or the seat has been folded.
  • The code can be set by a low battery or a voltage spike during jump-starting, so check for other low-voltage codes before condemning parts.
  • Never use a standard ohmmeter on a live airbag circuit; always disconnect the battery and wait the specified time to avoid accidental deployment.
  • After any repair, the SRS module may require a scan tool to clear the crash data or perform a learn procedure, or the light will remain on.
  • A pretensioner that has already deployed in a collision will set this code, and the entire seat belt assembly must be replaced, not just the buckle.

Can I keep driving with B0078?

Because this fault can prevent the third-row right pretensioner from working in a crash, have it repaired promptly and avoid carrying passengers in that seat until the SRS light is resolved. Do not attempt to bypass or disable the circuit, as that can cause unexpected deployment or leave the system inoperative.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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