Code
U0173
HYUNDAI
U — Network/User
Lost Communication With “Restraints System Sensor D”
Views:
UK: 11
EN: 16
RU: 16
AI status
Completed
Completed
100%
Causes
- Open/short in CAN bus or sensor wiring harness
- Poor connector contact or corrosion at sensor or SRS control unit
- Failed restraints system sensor/module D
- Defective SRS control module or gateway module
- Low battery voltage or poor battery ground
- Intermittent wiring damage from seat movement or installation
Symptoms
- SRS / Airbag warning lamp illuminated
- Possible disablement of related restraint functions (seatbelt pretensioner/airbag) for the affected circuit
- Stored U0173 code and possibly other network communication codes
- Intermittent or permanent loss of module data in scan tool
- Vehicle may fail SRS system self-check
What to check
- Verify battery voltage and chassis/engine grounds (battery >12.2 V at key-on recommended)
- Scan for U0173 and other related codes (U0100, U0155, U0121, etc.) and read freeze frame/live data
- Visual inspection of connectors and wiring for sensor D and SRS ECU (seat area, under-seat harness, connector pins)
- Backprobe sensor connector and SRS module CAN/LIN pins to confirm presence of proper bus voltages
- Check for CAN bus continuity and proper termination (120 ohm across CAN H/L at two ends)
- Wiggle test wiring and connectors while monitoring communication to locate intermittent faults
Signal parameters
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V)
- Typical CAN differential voltage when active ≈ 1.5–2.5 V
- Supply voltage to sensor/module: battery voltage (approx 12 V key-on)
- Module ground resistance: low and stable (near 0 Ω to chassis)
- Communication rate: manufacturer-specific (check service manual for bus speed)
Diagnostic algorithm
- Record all related stored codes and freeze frame data with an OEM-capable scan tool.
- Inspect visually: check sensor D connector, wiring for damage, pin corrosion or bent pins. Pay attention to under-seat areas and seat harness routing.
- Verify battery voltage and main grounds. Recharge or replace battery if voltage is low and retest.
- With ignition ON, backprobe the sensor D CAN (or LIN) and power/ground pins. Confirm proper supply voltage and expected CAN voltages (see signal_params).
- Check CAN continuity and termination resistance between CAN_H and CAN_L at the network ends (approx 60 ohm measured at a node; 120 ohm across bus ends).
- Perform wiggle tests on harnesses/connectors while monitoring for loss of communication or new codes.
- If wiring and power/ground check good but no communication, try swapping or reconnecting the sensor/module D if accessible and safe to do so (follow SRS safety procedures).
- If module swap not possible or communication still fails, inspect/replace connectors or repair wiring as required per wiring diagram.
- If wiring and sensor are confirmed good, suspect SRS control module or gateway — consult service manual for reprogramming or replacement instructions.
- After repairs, clear codes and verify that U0173 does not return and that SRS lamp functions normally. Perform a full SRS self-test using scan tool.
Likely causes
- Corroded/loose connector at sensor D or SRS ECU
- Wiring harness damaged (chaffing, broken conductor) between sensor and SRS module
- Sensor/module D internal failure
- CAN bus termination or wiring fault (short to battery/ground)
- Low voltage condition preventing module communication
Fault status
Status
Lost communication with Restraints System Sensor D — the restraints sensor/module is not responding on the vehicle communication bus. Inspect wiring, connectors, power/ground, and the SRS module for faults.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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