U0478: SRS Sensor H Data Invalid
The U0478 code indicates that the airbag control module (SDM) has received invalid, corrupt, or implausible data from the H sensor in the Supplemental Restraint System (SRS). This is a network communication code (U0xxx), meaning the issue lies in data transmission over the CAN or LIN bus, not necessarily a sensor failure. The SRS includes impact sensors, seat occupancy sensors, belt pretensioners, and other passive safety components.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty SRS sensor H (impact, occupancy, or position sensor)
- Electromagnetic interference or noise on the communication bus
- Abnormal resistance in CAN/LIN wiring due to corrosion, oxidation, or physical damage
- Sensor H connector with bent, corroded, or poorly sealed pins
- Internal failure of the airbag control module (SDM) misinterpreting data
- Voltage variation or unstable ground reference at the sensor module
- Outdated or corrupted control module software
- Moisture or water intrusion into the sensor connector or module
3. Symptoms You Will Notice
- Airbag warning light illuminated
- SRS system inoperative or disabled
- Possible no communication with scan tool
- Intermittent or no deployment of airbags
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data
Inspect sensor H connector for corrosion, bent pins, or moisture
Check CAN/LIN bus wiring for damage, shorts, or high resistance
Test sensor H resistance and voltage supply per manufacturer specs
Verify ground integrity at sensor and SDM
Update SDM software if available
Replace sensor H if all wiring and power checks pass
If code persists, replace SDM
5. Frequently Asked Questions
Is it safe to drive?▼
No, driving with this code is not recommended as the airbag system may not deploy in a crash, increasing injury risk.
How much does it cost to fix?▼
Repair costs range from $100 to $600, depending on whether it's a wiring fix, sensor replacement ($50-$200), or SDM replacement ($200-$600).