U0173 — Data bus: supplementary restraint system (SRS) sensor D – no communication
Introduction:
The diagnostic trouble code (DTC) U0173 indicates a communication problem between the vehicle’s electronic control units (ECUs) and the **Supplementary Restraint System (SRS)** sensor D. Essentially, this means that the vehicle’s safety system detects that the sensor responsible for monitoring specific crash data is not transmitting information properly.
Please note that **labeling and terminology may vary** slightly between vehicle manufacturers, but the core issue remains the same: a communication failure related to the SRS sensor D.
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**Fast Facts**
– System affected: SRS (Supplementary Restraint System) communications
– Severity: Moderate — may impair safety features but not necessarily prevent vehicle operation
– Main symptoms: Warning light for airbag or SRS may illuminate, possible DTC stored
– Driveability: Yes — vehicle can generally be driven, but safety systems may be compromised
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Manufacturer variations for trouble code U0173
Despite the same fundamental classification, automotive manufacturers often assign different labels or code identifiers within their distinct diagnostic systems. For U0173, known variations include:
– **Toyota:** C1773 or C1773-89 (varies by model)
– **BMW:** 00571, 00575, or similar codes linked to CAN bus communication issues within the SRS
– **Audi/VW:** 9350, 9351, or related codes indicating communication faults
– **Hyundai/Kia:** U0173 or U0237 (both can relate to communication faults with the SRS sensors)
*Note:* Always cross-reference manufacturer-specific repair manuals or diagnostic tools for precise label information.
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What does trouble code U0173 mean?
When your vehicle’s ECU (Engine Control Unit) detects **U0173**, it signifies that the **sensor D within the SRS system** has stopped communicating. Think of the SRS sensors as vital messengers; they provide crash data to the vehicle’s safety systems, enabling deployment of airbags and seatbelt pretensioners if needed.
The **ECU’s monitoring function** includes checking the communication signals over the vehicle’s CAN (Controller Area Network) bus. If the sensor D’s data line drops out or becomes erratic, the ECU interprets this as a fault and triggers the U0173 code.
Typically, this code appears in contexts such as **post-accident inspections**, **after battery disconnections or replacements**, or if components in the SRS wiring harness are damaged or faulty. It may also be caused by **intermittent connection issues** in the sensor or its wiring.
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Severity and risks of trouble code U0173
**U0173** is classified as a **moderate severity** diagnostic trouble code. While it does not necessarily disable the vehicle’s basic operation, it carries important safety implications:
– The **SRS system may not activate** in the event of an accident, reducing occupant protection.
– The **airbag warning light** on the dashboard is typically illuminated, alerting the driver to a potential safety concern.
– Powertrain or driving performance is usually unaffected, but ongoing issues could result in **unreliable safety system deployment**.
**Can the vehicle be driven with this code?**
Yes, in most cases, the vehicle can be driven. However, it is strongly advised to **diagnose and repair** the problem promptly to ensure the **full safety systems are operational**.
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Symptoms of trouble code U0173
The presence of **U0173** may not always produce obvious driving symptoms outside of the warning lights and DTCs in the vehicle’s onboard diagnostics. However, some common signs include:
– **Illumination of the SRS warning light or airbag warning light** on the dashboard.
– Possible **erratic or no communication responses** during diagnostic scans.
– **Intermittent or failed deployment of safety airbags** in the event of an accident (though rare as a different fault usually causes that).
– **Trouble codes stored in the SRS system** which may be flagged during a professional diagnosis.
Many vehicle owners may notice only the dashboard warning light, making **professional diagnosis essential** to confirm the exact cause.
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Most likely causes of trouble code U0173
**Introduction:**
The causes behind **U0173** generally revolve around communication interruptions between the vehicle’s **SRS sensors** and the **Vehicle’s Central Control Modules**. Among these causes, some are more common than others, especially in vehicles with age or prior repairs.
**Probable causes include:**
1. **Faulty or damaged SRS sensor D** — the sensor itself may have become defective or failed over time due to wear or impact.
2. **Corroded or loose wiring connections** — especially at the sensor connector or along the data bus wiring harness, which can lead to intermittent or lost communication.
3. **Damaged or shorted wiring harnesses** — physical damage from wear, rodents, or improper repairs can lead to communication faults.
4. **Faulty or failed SRS control module** — if the module responsible for processing sensor data malfunctions, communication issues may arise.
5. **Failed or disturbed CAN bus connections** — issues on the vehicle’s communication network, such as short circuits or broken bus lines, can impact sensor communication.
6. **Previous crash or SRS deployment** — which may have damaged sensors or wiring that require replacement or reprogramming.
7. **Battery or power supply issues** — voltage drops or electrical surges can temporarily disrupt communication.
**Note:** these causes are ordered from the most common to less frequent, but actual diagnosis should be performed to confirm.
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How to diagnose trouble code U0173
Diagnosing U0173 involves a systematic approach to identify where the communication failure originates. Here are some **generic diagnostic steps**:
1. **Visual inspection:** Check the wiring harness, connectors, and sensor D for any obvious signs of damage, corrosion, or disconnection.
2. **Read any stored codes and freeze frame data:** Use an advanced scan tool to view related codes and data snapshots.
3. **Verify the dashboard warning lights:** Confirm whether the SRS or airbag warning indicator is active.
4. **Check live data:** Observe the communication signals from the sensor via the diagnostic scanner, if available.
5. **Inspect wiring continuity:** Use a multimeter or oscilloscope to test the integrity and connectivity of the wiring between the sensor and control modules.
6. **Test sensor D resistance or signal output:** Refer to manufacturer specifications to confirm if the sensor’s electrical parameters are within acceptable ranges.
7. **Assess network communications:** Examine the vehicle’s CAN bus lines for proper voltage levels and absence of shorts or opens.
8. **Perform a module reset or reprogramming:** This may be necessary after repairs or to clear coding errors, as per manufacturer instructions.
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Possible repairs for trouble code U0173
Once the cause is identified, repairs can be performed accordingly. The type and complexity of repairs vary, but typical fixes include:
– **Replacing or repairing the faulty SRS sensor D:** *Basic repair*, suitable for DIY if you are comfortable with vehicle electronics.
– **Re-securing or replacing damaged wiring harnesses or connectors:** *Basic repair*, often requires inspection and replacement of affected cabling.
– **Repairing or replacing the entire wiring harness:** *Requires professional skills* for proper installation and routing.
– **Resetting or reprogramming the SRS control module:** *Professional repair*, involves specialised diagnostic equipment and knowledge.
– **Replacing the SRS control module:** *Professional repair*, usually as a last resort after confirming module failure.
– **Addressing CAN bus network issues:** *Requires professional diagnosis*, and repairs could involve replacing control modules, wiring, or addressing electrical shorts.
Always ensure repairs are performed with appropriate safety precautions, especially when working with airbag components.
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Vehicles commonly associated with trouble code U0173 in Europe
In Europe, **U0173** appears across various vehicle brands. While specific data on all models is limited, some of the more common brand groupings include:
– **Toyota:** Several models, especially those equipped with advanced CAN bus systems.
– **BMW:** E-Series, F-Series, and other recent models which utilize complex electronic communication networks.
– **Audi / Volkswagen / SEAT / Škoda:** Models from various years that use the CAN data bus for SRS systems.
– **Hyundai / Kia:** Modern vehicles with integrated electronic systems prone to communication faults.
Note: The prevalence of this code can vary widely depending on vehicle age, usage history, and previous repairs.
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Frequent mistakes with trouble code U0173
**Introduction:**
Diagnosing and repairing U0173 requires attention to detail to avoid common pitfalls that can prolong the repair or miss underlying issues.
**Common mistakes include:**
– **Ignoring wiring and connector inspections:** Assuming a sensor fault without checking wiring integrity is a frequent mistake.
– **Replacing sensors prematurely:** Swapping parts without confirmation of failure often leads to unnecessary costs.
– **Overlooking CAN bus wiring issues:** Communication faults may be due to network problems rather than individual sensors.
– **Failing to clear codes after repair:** Not resetting the ECU to verify repair efficacy can leave unresolved faults.
– **Neglecting to verify power supply voltage:** Electrical issues upstream can cause communication errors, yet are sometimes overlooked.
– **Assuming all communication failures are sensor faults:** Faults in control modules or wiring can mimic sensor problems, so proper diagnosis is essential.
*Best practice:* Always follow an organized diagnostic process, cross-check data, and avoid assumptions.
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FAQ — trouble code U0173
Q1: Can this code disappear on its own?
A: Generally, U0173 will not resolve itself. Once a communication fault occurs, it remains until it is diagnosed and repaired. Clearing the code without addressing the underlying cause may cause it to return.
Q2: Can I keep driving with U0173?
A: Yes, the vehicle can usually be driven, but the safety system’s responsiveness might be compromised. It is strongly recommended to have the fault diagnosed and corrected promptly.
Q3: Why does the code return after clearing?
A: If the underlying issue—such as damaged wiring, faulty sensor, or electrical network problem—is not resolved, the code will reappear. Proper diagnosis and repair are essential to prevent recurring faults.