OBD-II trouble code
U0478: Invalid Data Received From Restraints System Sensor H
The airbag (restraints) control module still hears from restraints system sensor H, but the data is implausible or out of range and gets rejected. The link is alive; the values can't be trusted. Because this sensor informs airbag deployment, treat U0478 as safety-critical and diagnose it promptly.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $700
- DIY difficulty
- Shop recommended
What does U0478 mean?
The restraints (airbag) control module reads a full network of impact, acceleration, and side-pressure sensors to detect a crash and protect the occupants. 'Sensor H' is one specific sensor in that network — on vehicles equipped with many satellite sensors, the highest letters cover additional side or rear-side positions, with the exact identity set by the manufacturer. U0478 sets when a receiving module continues to receive messages from restraints system sensor H, but those messages contain invalid data — a value out of range, implausible, or inconsistent with the rest of the system — so the controller can no longer trust it.
As with the rest of this family, the sensor is still transmitting; it's the content that's wrong. That is the line between U0478 and the lost-communication code U0177, where sensor H has gone silent. Because a crash sensor feeding bad numbers is a safety risk in both directions — an unwanted deployment or a missed one — the restraints module stores the fault, illuminates the airbag/SRS warning light, and can place the affected zone in a protective fault state.
Common causes are the usual signal-corrupters: a poor ground or low system voltage; corroded, loose, or moisture-damaged connectors at the sensor's location; chafed or fatigued wiring; a sensor drifting out of range or failing; or a configuration/software issue after a sensor or module was replaced without being programmed to the vehicle. If U0477 (sensor G) is present at the same time, look for a shared cause feeding both. Sensor H being the last in the lettered set, its presence often accompanies a wider restraints or bus problem, so scan for companion codes. The vehicle usually drives normally, hiding the reduced protection. Have U0478 diagnosed by a technician equipped to work safely on airbag circuits, since restraint wiring can trigger an accidental deployment if mishandled.
Common causes
- Corroded, loose, or moisture-damaged connector at restraints sensor H
- Water intrusion at a low or rear-side sensor mounting location
- Poor ground or low system voltage
- Chafed or fatigued wiring corrupting the sensor's data
- Sensor H drifting out of range or internally failing
- Sensor or restraints module replaced without correct programming/configuration
- Shared power/ground/bus fault (especially if U0477 or other restraints codes are set)
- Connector disturbed during collision, trim, or interior repair
Symptoms
- Airbag/SRS warning light on, often with a service-airbag message
- Restraints system fault state; zone deployment behavior may be affected
- Companion restraints or network codes stored with U0478 (often U0477)
- Intermittent setting over rough roads (connector/wiring related)
- Vehicle otherwise starts and drives normally
Diagnostic steps
- 1.Scan the restraints/SRS module and all modules; record every code. Follow safe SRS procedure — disconnect the battery and wait the specified time before handling airbag circuits.
- 2.Check for companion restraints codes (U0477 and other sensors) — several codes together point toward a shared power/ground/bus cause.
- 3.Locate restraints sensor H for the specific vehicle using factory service information.
- 4.Load-test the battery and verify charging voltage and the module's grounds.
- 5.Inspect the sensor H connector and harness for corrosion, moisture, backed-out terminals, and chafing.
- 6.Confirm the sensor and module are configured to the vehicle, especially after a recent replacement.
- 7.If power, ground, and wiring are good but data stays invalid, replace sensor H with the correct part and clear codes per factory procedure.
Repair cost
$100 – $700
Cost depends on the cause. Diagnosis usually runs $100-$200. Correcting low voltage, a bad ground, or a connector is often $150-$450. Reprogramming or configuring the sensor/module is typically $100-$350. Replacing restraints system sensor H with any required programming typically runs $200-$600+ depending on the sensor and its location. If a single shared fault is driving several restraints-sensor codes at once, fixing it can be far cheaper than replacing sensors. On any safety system, diagnose before replacing.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with airbag / srs crash sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.