U0174 is a generic OBD-II network communication diagnostic trouble code indicating that communication with the Restraint System Sensor Module has been lost. This module may be involved in monitoring crash-related sensors and providing information to the restraint system control unit.
Depending on the vehicle, the module may be identified by different manufacturer-specific names and may communicate with the airbag or restraint control system through a CAN network. The exact module location, wiring, network architecture, and diagnostic procedure vary by manufacturer, model, and model year.
U0174 Code Details
Code: U0174
Meaning: Lost Communication With Restraint System Sensor Module
Type: Generic OBD-II Network Communication Code
Main System: Restraint / Airbag Communication Network
Symptoms of U0174
- Airbag or SRS warning light may illuminate.
- Supplemental restraint system may report a fault.
- Scan tool may be unable to communicate with the affected sensor module.
- Multiple communication-related U-codes may be stored.
- Crash or restraint-related information may be unavailable.
- Airbag system self-test may fail.
- The restraint control module may report missing sensor communication.
- Some restraint-system functions may be disabled.
Common Causes of U0174
- Low battery voltage.
- Blown fuse supplying the restraint sensor module.
- Missing module power supply.
- Poor or damaged module ground.
- Open CAN High or CAN Low circuit.
- Shorted or damaged CAN wiring.
- Loose or corroded electrical connector.
- Damaged terminals or poor terminal tension.
- Water intrusion.
- Harness damage after an accident or interior repair.
- Another control module affecting the communication network.
- Faulty restraint system sensor module.
How Serious Is U0174?
U0174 should be considered a high-priority diagnostic fault because it involves the vehicle's restraint system. Depending on the vehicle architecture, loss of communication with a restraint sensor module may affect the operation or monitoring of airbags, pretensioners, crash detection, or other SRS functions.
Do not assume that the airbags will operate normally while a significant SRS communication fault remains unresolved. Follow the manufacturer's safety procedures before working on any restraint-system wiring or components.
Can You Drive With U0174?
The vehicle may still start and drive normally with U0174, but this does not mean the restraint system is operating correctly. If the SRS or airbag warning light is illuminated, the fault should be diagnosed as soon as possible because some restraint functions may be unavailable.
How to Diagnose U0174
1. Perform a Complete System Scan
Use a professional scan tool capable of accessing the SRS, airbag, restraint, and other vehicle modules. Record U0174 and all related codes before clearing anything.
Pay particular attention to additional U-codes, voltage codes, SRS codes, or sensor communication faults because they may identify the actual source of the network problem.
2. Check Battery and Charging Voltage
Verify battery condition and charging-system voltage. Low or unstable voltage can cause restraint modules and other electronic control units to reset or temporarily disappear from the CAN network.
3. Check Module Fuses
Use the vehicle-specific fuse diagram to identify every fuse supplying the restraint sensor module and related SRS components. Test the appropriate circuits rather than relying only on visual inspection.
4. Test Power and Ground
Verify the required power supplies and ground circuits at the affected module according to manufacturer specifications. A missing power or ground circuit can make a functional module appear to be offline.
5. Inspect Connectors and Wiring
Inspect the module connector and surrounding harness for corrosion, damaged terminals, loose connections, water intrusion, crushed wiring, or previous repair work.
Pay particular attention to areas affected by previous collision repairs because restraint-system wiring can be damaged during body or interior work.
6. Check CAN Communication Circuits
If the affected restraint sensor module communicates through CAN, inspect CAN High and CAN Low circuits for opens, shorts, excessive resistance, damaged insulation, or poor connections.
The exact CAN pins and network configuration are manufacturer-specific. Do not apply a generic pinout to a vehicle without confirming the wiring diagram.
7. Check for Another Module Affecting the Network
If several control modules report communication failures, investigate common power, ground, and CAN network circuits before replacing the restraint sensor module.
8. Test the Restraint System Sensor Module
If power, ground, fuses, connectors, and network communication are verified, follow the manufacturer's diagnostic procedure to determine whether the restraint system sensor module has an internal failure.
U0174 Oscilloscope Signal Patterns
An oscilloscope can be useful when U0174 involves an intermittent or distorted CAN communication problem. It can help identify abnormal network activity that may not be visible during a basic scan.
Normal / Active CAN
Normal: Stable CAN communication with consistent signal transitions.
Abnormal / Distorted
Abnormal: Noise, distorted transitions, or intermittent communication may indicate a network or wiring problem.
Inactive / No Communication
Inactive: Expected communication is absent at the tested network point.
Important: These are simplified diagnostic illustrations, not manufacturer-specific waveform specifications. Actual CAN High and CAN Low voltage levels, timing, termination, and signal behavior must be compared with the specifications for the exact vehicle.
U0174 Diagnostic Signal Flow
↓
Restraint System Sensor Module
↓
CAN-H / CAN-L
↓
SRS / Airbag Control Module
↓
Crash Detection & Restraint Functions
U0174 OBD Live Data
Available parameters depend on the vehicle and scan tool. Where supported, useful information may include module communication status, system voltage, sensor status, crash-related sensor information, network status, and restraint-system data.
Live data should be combined with direct electrical testing because an intermittent connector, damaged harness, or network fault may not remain active while the vehicle is stationary.
Common Repairs for U0174
- Repair missing module power supply.
- Repair poor or damaged module ground.
- Replace a failed fuse after identifying the cause.
- Repair damaged CAN High or CAN Low wiring.
- Repair loose or corroded connectors.
- Repair damaged electrical terminals.
- Correct water intrusion.
- Repair collision-damaged restraint wiring.
- Repair another module that is disrupting CAN communication.
- Repair or replace the restraint system sensor module when internal failure is confirmed.
- Perform required programming, configuration, or calibration after module replacement.
U0174 Repair Cost
- Electrical/network diagnosis: approximately $100–$250+.
- Fuse or wiring repair: approximately $75–$300+.
- Connector or terminal repair: approximately $80–$300+.
- CAN network repair: approximately $100–$400+.
- Sensor module repair: approximately $150–$700+.
- Module replacement and programming: approximately $400–$1,500+ depending on the vehicle.
These are general estimates only. Actual costs vary according to vehicle, parts availability, labor rates, module design, programming requirements, and manufacturer procedures.
Common Repair Mistakes
- Replacing the restraint sensor module before checking power and ground.
- Ignoring low battery voltage.
- Failing to inspect connectors after a collision.
- Testing only one CAN communication circuit.
- Assuming U0174 automatically means the module is defective.
- Ignoring other communication codes stored in the vehicle.
- Using incorrect wiring or pinout information.
- Working on SRS wiring without following manufacturer safety procedures.
- Installing a replacement module without required programming or configuration.
Related OBD-II Codes
- U0151 – Lost Communication With Restraints Control Module.
- U0154 – Lost Communication With Restraints Occupant Sensing Control Module.
- U0156 – Lost Communication With Information Center Module.
- U0155 – Lost Communication With Instrument Panel Cluster.
- U0100 – Lost Communication With ECM/PCM.
- U0121 – Lost Communication With Anti-Lock Brake System (ABS) Control Module.
- U0140 – Lost Communication With Body Control Module.
FAQ About U0174
What does U0174 mean?
U0174 means Lost Communication With Restraint System Sensor Module. It indicates that the vehicle network has detected a loss of communication with the affected restraint-system sensor module.
Can a weak battery cause U0174?
Yes. Low or unstable system voltage can cause restraint modules to reset or stop communicating with the vehicle network.
Can CAN wiring cause U0174?
Yes. An open, shorted, damaged, or poorly connected CAN circuit can prevent the restraint system sensor module from communicating.
Does U0174 mean the airbag module is bad?
No. U0174 identifies a communication problem with the restraint system sensor module. Power, ground, fuses, connectors, wiring, and CAN communication should be tested before replacing any module.
Can a multimeter diagnose U0174?
Yes. A multimeter can be useful for checking power supplies, grounds, voltage, resistance, and certain wiring circuits. However, CAN communication faults may require an oscilloscope or advanced scan tool for accurate diagnosis.
Is an oscilloscope useful for U0174?
Yes. An oscilloscope can help identify abnormal CAN activity, electrical noise, distorted signals, intermittent communication, or a missing network signal when conventional testing does not identify the cause.
Can I replace the restraint sensor module myself?
Restraint-system components require special safety procedures. Some vehicles also require programming, configuration, initialization, or calibration after replacement. Follow the manufacturer service procedure and use appropriate SRS safety precautions.
Final Takeaway
U0174 is a generic OBD-II network communication code indicating lost communication with the Restraint System Sensor Module.
The most reliable diagnosis starts with battery voltage, fuses, module power and ground, connectors, CAN wiring, and a complete scan of all control modules. A restraint-system sensor module should not be replaced simply because U0174 is stored.
Because U0174 can involve the vehicle's airbag and restraint network, diagnosis should be performed carefully using the correct vehicle-specific wiring diagrams, safety procedures, and manufacturer specifications.