U0173
UniversalLost Communication With Restraints System Sensor D
The restraint control system is not receiving expected communication from Sensor D. Restraint sensors provide information used by the system to assess a crash and control protective devices. A communication fault does not prove the sensor itself has failed; wiring, connections, power, or another part of the communication path may be involved. The restraint warning light may come on, and some airbags or pretensioners may not work as intended.
⚠️ Before You Begin (Safety First)
Treat this as a safety-related fault and arrange prompt diagnosis by a qualified technician. Do not probe, disconnect, or repair airbag or pretensioner wiring, and do not bypass the restraint system. If the restraint warning light is on, occupant protection may be reduced in a crash. Follow the vehicle owner's manual for safety guidance.
Common Symptoms
- The airbag or restraint warning light may illuminate because the control system detects missing communication.
- Some airbags or seat-belt pretensioners may not operate as intended if the system cannot use the missing sensor information.
- Other restraint-system warnings or stored codes may appear if the same communication problem affects related functions.
- There may be no obvious driving symptoms; restraint-system faults can remain unnoticed until a warning appears or the system is checked.
Common Causes
- A damaged, loose, or corroded connection in Sensor D's communication path.
- Damaged wiring or a loss of power or ground affecting the sensor or its circuit.
- A fault within Sensor D, which needs testing before replacement is considered.
- A communication or control-module fault elsewhere in the restraint system.
- Low vehicle voltage or prior impact, water, or repair damage affecting restraint-system components or wiring.
Diagnostic Steps
- Note whether the restraint warning light is on and when it appeared; this helps a technician understand the fault's context.
- Look for obvious signs of collision damage, water intrusion, or disturbed trim near areas previously repaired, but do not remove trim or touch restraint-system wiring or connectors.
- If other electrical warnings or starting problems are present, mention them when booking diagnosis because shared voltage issues can affect communication.
- Arrange a restraint-system scan and diagnosis with a qualified technician; do not clear the code or attempt SRS circuit testing as a substitute for finding the cause.
When to Call a Professional
Use a scan tool that can access the restraint control system to confirm current and related codes, then follow the vehicle-specific diagnostic procedure to check communication, power, grounds, connectors, and wiring. Do not replace Sensor D based on this code alone. SRS circuit testing and repairs should follow model-specific safety procedures.
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Commonly Asked Questions
Does U0173 prove that Sensor D needs replacement?
No. It indicates lost communication with Restraints System Sensor D, not a confirmed sensor failure. Wiring, connections, power, grounds, or another part of the communication path may be responsible.
Can I keep driving with this code?
The code may not affect normal vehicle handling, but restraint protection could be reduced in a crash. Arrange prompt professional diagnosis and follow the owner's manual for vehicle-specific guidance.
Why might there be no noticeable symptoms?
A communication fault may not change how the vehicle drives. The restraint warning light or a scan of the restraint control system may be the only indication.
Can a basic engine-code reader diagnose U0173 fully?
Not necessarily. Diagnosis generally requires a scan tool able to access the restraint control system and retrieve related module information.
Is it safe to inspect the sensor wiring myself?
Limit checks to looking for obvious external damage without touching connectors or wiring. Do not probe, disconnect, or repair airbag or pretensioner circuits; refer those tasks to a qualified technician.
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