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Home / DTC / U017B — Lost Communication With Restraints System Sensor L

U017B — Lost Communication With Restraints System Sensor L

Detailed page for trouble code U017B.

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Code

U017B

Generic U — Network/User

Lost Communication With Restraints System Sensor L

Brand: Generic
Type: U — Network/User
Views: UK: 16 EN: 33 RU: 18
AI status
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Page language: EN

Causes

  • Damaged or disconnected wiring or connector to the left restraints sensor
  • Faulty left restraints (SRS) sensor or internal sensor electronics
  • Faulty restraint control module (RCM/SRS module) or other network module
  • CAN/LIN bus faults: short to voltage, short to ground, open circuit, or excessive bus loading
  • Poor battery voltage or intermittent power/ground to sensor or modules
  • Improper module programming or incompatible replacement module

Symptoms

  • SRS/airbag warning lamp illuminated or DTC indicator on instrument cluster
  • Possible disablement of some restraints functions (dependent on vehicle)
  • Stored or active U017B and possibly other network or SRS-related codes
  • No obvious mechanical driveability symptoms (communication fault only)
  • Intermittent fault reappearing after clearing codes or after vibration

What to check

  • Read and record all SRS and network-related codes from all modules with a capable scan tool
  • Check battery voltage and charge state; test for stable vehicle supply during diagnostics
  • Visually inspect connectors and wiring for the left restraints sensor (pins, corrosion, damage)
  • Perform wiggle test on harness and connectors while monitoring network messages or live data
  • Check power and ground at the left restraints sensor connector with key on
  • Verify CAN/LIN bus health: measure resistance across bus termination (~60 ohms for CAN), check for shorts to battery/ground

Signal parameters

  • Expected periodic SRS sensor message (frequency varies by make; often 5–20 Hz) — should be present on vehicle network
  • CAN bus idle voltages: both CAN_H and CAN_L near 2.5 V (recessive); dominant state typically CAN_H ≈ 3.5 V and CAN_L ≈ 1.5 V
  • Typical CAN differential voltage when dominant ≈ 1.5–2.5 V (varies by manufacturer)
  • Termination resistance across CAN_H and CAN_L ≈ 60 ohms (two 120-ohm terminators in parallel)
  • Power supply to sensor (if powered directly) typically battery voltage with ignition on (~11–14 V); ground should be low resistance
  • No RX/TX errors or high error counters in related modules' network status messages

Diagnostic algorithm

  1. Retrieve all stored DTCs and freeze-frame data from SRS and network modules. Document related codes and time stamps.
  2. Verify vehicle battery is fully charged and engine off/current state per manufacturer procedure. Reproduce condition if intermittent.
  3. Inspect the left restraints sensor connector and harness for physical damage, moisture, or corrosion. Repair any visible damage.
  4. Check for power and ground at the sensor connector with a multimeter. Backprobe if necessary and safe; do not deploy SRS components.
  5. Using a scan tool, monitor live data/messages for the left sensor. Note whether its periodic messages are present and whether they drop out.
  6. Wiggle the harness and connectors while watching live data/messages to find intermittent opens or shorts.
  7. Measure CAN_H and CAN_L with a scope or DMM to confirm idle voltages and proper dominant/recessive transitions when messages transmit.
  8. Check termination resistance across CAN lines (~60 ohms). Repair or replace damaged terminators or wiring if out of spec.
  9. If wiring and connectors check OK and sensor has no power/ground issues but no messages are present, replace the left restraints sensor with a known-good unit (or swap with right sensor if identical and allowed) to verify communication restoration.
  10. If replacement sensor does not restore communication, inspect and test the SRS module and other modules on the same network segment; reprogram or replace module if proven faulty.
  11. After repairs, clear codes and perform complete SRS system checks and any required module initialization/seatbelt/relearn procedures per manufacturer service instructions.
  12. Confirm fault does not return during road test or after cycling ignition and normal vehicle operation.

Likely causes

  • Connector at left restraints sensor is loose, corroded or pushed out
  • Wiring harness damaged by impact or chafing near wheel well or seat
  • Left restraints sensor has failed (electrical or internal)
  • Termination resistor or CAN bus wiring is open/shorted causing network dropout
  • SRS module lost power, ground, or was replaced and not configured

Fault status

⚠️ Status
Control module lost communication with left restraints system sensor. Sensor messages not detected or intermittent; SRS/airbag fault stored.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-4.0 hours

Similar codes

U0100 U0121 U0126 U0173 U017A B0001
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