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DTC codes / U01xx · Lost communication with a control module / U017F

U017FLost Communication With Seat Belt Pretensioner Module B

U017F is a generic network communication code indicating that the vehicle's main control modules have lost contact with the seat belt pretensioner module B over the controller area network (CAN) bus. The computer has detected that expected periodic messages from this safety module are no longer arriving, which can disable the pretensioner's ability to tighten the seat belt during a collision.

SystemNetwork
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaLost communication with a control module

Symptoms you may notice

  • The supplemental restraint system (SRS) warning light or airbag light is illuminated on the dashboard.
  • A message such as 'Service Airbag' or 'Check Restraint System' may appear on the driver information center.
  • The seat belt pretensioner for the affected seating position may not deploy in a crash, increasing injury risk.
  • Other restraint system functions, such as seat belt reminder chimes or passenger sensing, may behave erratically.
  • Often no symptoms besides the warning light, because the module can fail internally without affecting normal driving.

Common causes, most likely first

  1. A faulty seat belt pretensioner module B, often due to internal electronics failure or water intrusion.
  2. Damaged or corroded wiring harness or connector at the pretensioner module, commonly from seat movement or moisture.
  3. A blown fuse or poor ground connection supplying power to the pretensioner module.
  4. CAN bus communication line faults, such as an open, short, or high resistance in the twisted pair wiring.
  5. A malfunctioning central restraint control module (airbag control module) that is not sending or receiving messages correctly.
  6. Low battery voltage or a weak charging system causing intermittent module dropouts.
  7. Aftermarket accessories or improper previous repairs that disturbed the SRS wiring or connectors.

How to diagnose and fix it

  1. Verify battery voltage and charging system output, as low voltage can cause communication codes; recharge or replace the battery if needed.
  2. Inspect the seat belt pretensioner module B connector and wiring for corrosion, damage, or loose pins, especially under the seat or trim panels.
  3. Check the fuse and ground connections for the pretensioner module circuit using a multimeter and wiring diagram.
  4. Use a scan tool to perform a network communication test and check for other codes that may indicate a broader CAN bus issue.
  5. Measure resistance and continuity on the CAN bus lines at the pretensioner module connector to rule out wiring faults.
  6. If wiring and power are good, substitute a known-good pretensioner module B and clear codes to see if communication returns.
  7. After repairs, clear codes and perform a road test to confirm the module communicates and the SRS light stays off.

Before replacing the pretensioner module

  • A common oversight is assuming the pretensioner module itself is dead when the real problem is a chafed wire under the seat that shorts only when the seat is moved.
  • This code can be set by a weak battery or poor ground even if the module is healthy, so always load-test the battery and check grounds first.
  • Some vehicles require reprogramming or initialization of the pretensioner module after replacement, which a generic scan tool cannot perform.
  • U017F often appears alongside other U-codes if the CAN bus is compromised, so diagnosing the network as a whole can reveal the root cause.
  • The seat belt pretensioner is a pyrotechnic device; never probe its connectors with a powered test light or ohmmeter without following manufacturer safety procedures.

Can I keep driving with U017F?

It is not safe to drive with an active U017F code because the affected seat belt pretensioner may not deploy in a collision, compromising occupant protection. Have the vehicle diagnosed and repaired by a qualified technician before driving, and avoid any situation that could trigger a crash.

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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