U0174

Universal

Lost Communication With Restraints System Sensor E

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Advanced
High Severity

The restraint system uses sensor information to help assess and manage occupant protection. This code means the vehicle detected that it could not communicate with Restraints System Sensor E. The exact role of that sensor varies by vehicle. The airbag or other restraint functions may be affected, although the code alone does not confirm that a particular component has failed.

Report an error with this code

⚠️ Before You Begin (Safety First)

Treat this as a safety-related fault. Have the restraint system checked promptly, especially if an airbag or restraint warning is illuminated. Do not probe, unplug, or bypass restraint-system wiring or connectors; incorrect handling can cause injury or further damage. The code alone does not establish whether the vehicle is safe to drive, so follow the vehicle’s warning instructions and do not drive if the vehicle has collision damage or another condition that makes it unsafe.

Common Symptoms

  • An airbag or restraint-system warning may illuminate if the vehicle detects a communication fault.
  • The vehicle may have no noticeable symptoms during normal driving because the fault concerns restraint-system communication.
  • Some restraint functions may be unavailable or may not operate as intended if the required sensor information is missing; the specific effect depends on the vehicle.
  • A scan tool may show this code along with other communication or restraint-system codes.

Common Causes

  • A loose, damaged, corroded, or poorly connected electrical connection in the communication path to the sensor.
  • Damaged wiring or a network communication fault between the sensor and restraint-system controller.
  • A problem with power or ground supplied to the sensor or related restraint-system components.
  • A fault in Restraints System Sensor E or in a related control module; the code alone does not prove either component has failed.
  • Low or unstable vehicle voltage may contribute to communication faults in some circumstances.

Diagnostic Steps

  1. Note any airbag or restraint warning lights and record all codes with a scan tool that supports the restraint system; related codes can help identify whether the issue is local or part of a wider communication problem.
  2. Check the vehicle’s owner information for instructions associated with any restraint-system warning, and arrange prompt diagnosis if a warning is present.
  3. With the vehicle safely parked, look for obvious collision damage, water intrusion, or damaged wiring that is visible without touching restraint-system connectors; these clues can help a technician trace the fault.
  4. If there are signs of weak battery operation, have the battery and charging system checked; unstable voltage can affect electronic communication.
  5. Do not unplug or test SRS connectors, probe restraint circuits, or clear the code as a substitute for diagnosis. Have a qualified technician perform system-specific electrical tests.

When to Call a Professional

Use a scan tool that can read restraint-system codes and communication status, then compare results with model-specific service information. A qualified technician can check the relevant power, ground, connectors, wiring, and network communication using the vehicle’s prescribed SRS safety procedures. Confirm the cause before replacing a sensor or module.

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Commonly Asked Questions

Does U0174 prove that Restraints System Sensor E is defective?

No. It reports lost communication with that sensor. Wiring, connectors, power, ground, network communication, or a related module can also cause the condition.

Can the vehicle seem normal while this code is present?

Yes. A communication fault may not change how the vehicle drives, but some restraint functions may be affected without an obvious driving symptom.

Should I replace the sensor first?

No. The fault should be diagnosed before parts are replaced. A qualified technician should check communication and the relevant electrical circuits using vehicle-specific SRS procedures.

Can I inspect or unplug the sensor connector myself?

Do not unplug, probe, or handle restraint-system connectors. SRS circuits require prescribed safety procedures, and incorrect testing can cause injury or damage.

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