U0173 — Data Bus: Supplementary Restraint System (SRS) Sensor D – No Communication #

Note: The wording of this code description may vary depending on the vehicle manufacturer (OEM).

• Mercedes-Benz: Data Bus: SRS Sensor D – No Communication
• Ford: Lost Communication With SRS Sensor D
• Honda: SRS Sensor D Unable to Communicate
• Toyota: CAN Communication Error: SRS Sensor D

Summary of Code U0173 #

The U0173 diagnostic trouble code (DTC) is triggered when the vehicle’s main control module, known as the Powertrain Control Module (PCM), or body control module (BCM), detects a loss of communication with the Supplementary Restraint System (SRS) Sensor D through the vehicle’s data bus network. The SRS is a crucial safety system designed to deploy airbags or other restraint features in the event of a collision. The “data bus” refers to the network of wires and connectors that transmit information between different modules in your vehicle, commonly using protocols like CAN (Controller Area Network). When communication fails specifically with Sensor D, it can compromise the accuracy or readiness of the airbag system, which is why this code should not be ignored.

Common Symptoms for Code U0173 #

When U0173 is set, the vehicle may display subtle or obvious signs. The most frequent symptom is the airbag warning light illuminating on the dashboard, signaling a potential issue with the SRS. Other symptoms may be less apparent if the vehicle does not immediately deploy airbags unless needed, but could include:

• Airbag or SRS warning light on
• Warning messages such as “SRS Fault” or “Airbag System Service Required”
• Possible chime or alert tone
• Failure of airbags to deploy in a collision (in extreme cases)
• No other drivability symptoms in most cases

Most Likely Causes for Code U0173 #

There are several reasons why your vehicle may store a U0173 code. The following causes are arranged in order of frequency, based on typical OEM and field data:

1. Damaged or corroded wiring/connectors to SRS Sensor D or on the data bus
2. Faulty SRS Sensor D (internal failure)
3. Loose, disconnected, or damaged connectors at the SRS sensor or control modules
4. Faulty control module (e.g., SRS airbag control unit or BCM)
5. Network issues (CAN bus faults, short to ground, or open circuit)
6. Incorrectly performed repairs or modifications affecting wiring or the SRS system

Step-by-Step Diagnosis for Code U0173 #

Diagnosing U0173 requires careful, methodical steps to avoid accidental airbag deployment or further system damage. If you are not comfortable working with the SRS, always defer to a qualified technician. Here’s a recommended approach:

• 1. Retrieve codes and freeze frame data with an OBD-II/EOBD scan tool to confirm U0173 is active and note any related codes.
• 2. Visually inspect wiring and connectors at SRS Sensor D for damage, corrosion, or loose pins.
• 3. Check the data bus wiring (CAN wiring) in the harness for continuity, shorts, or opens using a multimeter.
• 4. Verify power and ground at the sensor and related modules using wiring diagrams.
• 5. Test the SRS Sensor D (per OEM procedure) for correct resistance or signal output if accessible.
• 6. Inspect the relevant control module (e.g., airbag control unit) for signs of water intrusion or fault.
• 7. Clear the codes and retest after each repair step to see if U0173 returns.
• 8. Consult OEM service information for any vehicle-specific checks or software updates.

Possible Repairs for Code U0173 #

Depending on the underlying cause found during diagnosis, several repairs may resolve U0173. Always follow OEM procedures and ensure the battery is disconnected before working on SRS components to prevent accidental airbag deployment.

• Repair or replace damaged wiring or connectors to SRS Sensor D
• Replace faulty SRS Sensor D
• Reconnect or properly secure loose connectors
• Repair or replace damaged CAN bus wiring
• Replace a faulty control module (airbag ECU or BCM), if confirmed defective
• Address water intrusion or corrosion issues at connectors or modules
• Install any available OEM software updates or recalibrations

Is It Safe to Drive With Code U0173? #

It is generally not recommended to drive with code U0173 present. While your car may still operate normally, the airbag system’s integrity is compromised. In the event of a collision, some or all airbags may fail to deploy, increasing the risk of injury. For your safety and that of your passengers, address this code as soon as possible and avoid unnecessary driving until repairs are completed.

Vehicles Most Commonly Affected by Code U0173 #

While U0173 can appear on any vehicle using a networked SRS system, it is most frequently reported on certain makes and models. This list is not exhaustive, but includes:

• Mercedes-Benz (various models, especially C-Class and E-Class)
• Ford (F-150, Focus, Explorer)
• Honda (Accord, Civic, CR-V)
• Toyota (Camry, Corolla, RAV4)
• Volkswagen (Passat, Golf)
• Chevrolet (Silverado, Malibu)
• Nissan (Altima, Rogue)

Common Mistakes & Best Practices for Code U0173 #

A few recurring errors can lead to misdiagnosis or incomplete repairs when dealing with U0173. To get it right the first time, keep these points in mind:

• Assuming the SRS Sensor D is faulty without first checking wiring and connectors
• Overlooking corroded or loose pins at connectors
• Disconnecting SRS components without following OEM safety precautions
• Neglecting to clear codes and retest after each step
• Skipping the check for related codes that may provide more context
• Using non-OEM parts that may not communicate properly on the data bus

Quick FAQ for Code U0173 #

Have more questions? Here are answers to common concerns:

• Q: Can I reset the code and ignore it if the light goes away?
  A: No. Even if the warning light disappears temporarily, the underlying communication issue may still be present. Always diagnose and repair the root cause to ensure your airbag system will protect you in an emergency.
• Q: Will disconnecting the battery clear the U0173 code?
  A: Disconnecting the battery may temporarily erase the code, but it will return if the communication problem persists. Proper diagnosis and repair are required.
• Q: Do I need a factory scan tool for this diagnosis?
  A: While a basic OBD-II/EOBD scanner can read and clear codes, a factory or advanced scan tool is often necessary to access SRS-specific data and perform in-depth diagnostics.