Code
U0172
Generic
U — Network/User
Lost Communication With Restraints System Sensor C
Views:
UK: 18
EN: 31
RU: 19
AI status
Completed
Completed
100%
Causes
- Open or shorted CAN/communication wiring between sensor and network
- Faulty or corroded connector at the sensor or wiring harness
- Sensor/module power or ground missing (fuse, relay, wiring)
- Failed restraints sensor/module (internal fault)
- Network transceiver or control module fault (ECU or gateway)
- Bus termination or wiring short (high resistance, short to battery/ground)
Symptoms
- Airbag/Restraints warning lamp illuminated
- Possible supplemental restraint system (SRS) messages or DTCs displayed
- Related systems reporting other network comm errors
- Occupant detection or seatbelt pretensioner functions disabled or unavailable
- No response from Restraints Sensor C when queried with a scan tool
What to check
- Use a scan tool to read all network and restraints-related codes and note freeze frame data
- Verify whether Restraints Sensor C appears on the network (module list) and can be queried
- Visually inspect wiring harness and connector for Sensor C for damage, corrosion, or pushed-out pins
- Check fuses and relays supplying the sensor/module
- Measure battery voltage at the sensor power pin and verify ground continuity
- Check CAN bus wiring for continuity and shorts between CAN-H/CAN-L and to battery or ground
Signal parameters
- Typical idle voltage on each CAN line: ~2.5 V (each line to ground)
- Dominant/recessive differential voltages: dominant ≈ 1.5 V–3.5 V differential, recessive ≈ 0 V differential
- Nominal bus speeds: 125 kbps, 250 kbps or 500 kbps depending on vehicle design
- Termination resistance: ~60 Ω across CAN-H and CAN-L with key on
- Expected voltage at sensor power pin: battery voltage (~12 V) with ignition on
- Expected ground resistance: low (
Diagnostic algorithm
- Retrieve all DTCs from all modules and record freeze frame and history. Note related U-codes and any repeated events.
- Attempt to communicate with Restraints Sensor C using a scan tool. Confirm 'no response' or 'timeout'.
- Inspect sensor connector and harness for visible damage, corrosion, pushed pins or signs of moisture. Repair as needed.
- Check power and ground to the sensor: verify fuse integrity, measure battery voltage at the sensor power terminal, and check ground continuity to chassis.
- Verify CAN bus health: check termination resistance (~60 Ω). Use a multimeter for continuity and an oscilloscope to verify CAN-H/CAN-L signals while the network is active.
- If bus is shorted or open, isolate sections of the harness (disconnect other modules or splice connectors) to locate the faulted segment.
- If wiring and power/ground are good, swap or bench-test the sensor/module (if permissible) or replace the sensor with a known-good unit and re-test communication.
- If sensor replacement does not restore communication, test the gateway/ECU transceiver and related modules for faults. Update or reflash module software if manufacturer service information indicates.
- After repair, clear DTCs, verify diagnostic readiness, and perform a test drive or functional verification to ensure the fault does not return.
- Document repairs and any module programming performed.
Likely causes
- Damaged or disconnected sensor connector or harness at sensor C
- Sensor C lost supply voltage or ground (blown fuse, disconnected power lead)
- Broken or high-resistance CAN-H or CAN-L wiring near sensor C
- Corroded pins causing intermittent contact
- Failed sensor/module electronics or CAN transceiver
Fault status
Status
Lost communication with Restraints System Sensor C on the vehicle network (no response or intermittent communication). This condition can disable restraint functions and will illuminate the SRS/warning indicator until communication is restored.
Repair difficulty: Medium
Diagnostic time: 1.5 - 3.0 hours
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Code
U0172
HYUNDAI
U — Network/User
Lost Communication With “Restraints System Sensor C”
Views:
UK: 11
EN: 21
RU: 19
AI status
Completed
Completed
100%
Causes
- Open or shorted CAN/communication wiring between sensor and network
- Faulty or corroded connector at the sensor or wiring harness
- Sensor/module power or ground missing (fuse, relay, wiring)
- Failed restraints sensor/module (internal fault)
- Network transceiver or control module fault (ECU or gateway)
- Bus termination or wiring short (high resistance, short to battery/ground)
Symptoms
- Airbag/Restraints warning lamp illuminated
- Possible supplemental restraint system (SRS) messages or DTCs displayed
- Related systems reporting other network comm errors
- Occupant detection or seatbelt pretensioner functions disabled or unavailable
- No response from Restraints Sensor C when queried with a scan tool
What to check
- Use a scan tool to read all network and restraints-related codes and note freeze frame data
- Verify whether Restraints Sensor C appears on the network (module list) and can be queried
- Visually inspect wiring harness and connector for Sensor C for damage, corrosion, or pushed-out pins
- Check fuses and relays supplying the sensor/module
- Measure battery voltage at the sensor power pin and verify ground continuity
- Check CAN bus wiring for continuity and shorts between CAN-H/CAN-L and to battery or ground
Signal parameters
- Typical idle voltage on each CAN line: ~2.5 V (each line to ground)
- Dominant/recessive differential voltages: dominant ≈ 1.5 V–3.5 V differential, recessive ≈ 0 V differential
- Nominal bus speeds: 125 kbps, 250 kbps or 500 kbps depending on vehicle design
- Termination resistance: ~60 Ω across CAN-H and CAN-L with key on
- Expected voltage at sensor power pin: battery voltage (~12 V) with ignition on
- Expected ground resistance: low (
Diagnostic algorithm
- Retrieve all DTCs from all modules and record freeze frame and history. Note related U-codes and any repeated events.
- Attempt to communicate with Restraints Sensor C using a scan tool. Confirm 'no response' or 'timeout'.
- Inspect sensor connector and harness for visible damage, corrosion, pushed pins or signs of moisture. Repair as needed.
- Check power and ground to the sensor: verify fuse integrity, measure battery voltage at the sensor power terminal, and check ground continuity to chassis.
- Verify CAN bus health: check termination resistance (~60 Ω). Use a multimeter for continuity and an oscilloscope to verify CAN-H/CAN-L signals while the network is active.
- If bus is shorted or open, isolate sections of the harness (disconnect other modules or splice connectors) to locate the faulted segment.
- If wiring and power/ground are good, swap or bench-test the sensor/module (if permissible) or replace the sensor with a known-good unit and re-test communication.
- If sensor replacement does not restore communication, test the gateway/ECU transceiver and related modules for faults. Update or reflash module software if manufacturer service information indicates.
- After repair, clear DTCs, verify diagnostic readiness, and perform a test drive or functional verification to ensure the fault does not return.
- Document repairs and any module programming performed.
Likely causes
- Damaged or disconnected sensor connector or harness at sensor C
- Sensor C lost supply voltage or ground (blown fuse, disconnected power lead)
- Broken or high-resistance CAN-H or CAN-L wiring near sensor C
- Corroded pins causing intermittent contact
- Failed sensor/module electronics or CAN transceiver
Fault status
Status
Lost communication with Restraints System Sensor C on the vehicle network (no response or intermittent communication). This condition can disable restraint functions and will illuminate the SRS/warning indicator until communication is restored.
Repair difficulty: Medium
Diagnostic time: 1.5 - 3.0 hours
Similar codes
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