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DTC codes / U04xx · Invalid data received from a module / U047C

U047CInvalid Data Received From Restraints System Sensor L

U047C is a generic communication fault indicating that a module on the controller area network (CAN) bus received invalid or corrupted data from the restraints system sensor designated as 'L'. The computer detected a message from that sensor that failed its internal plausibility or checksum validation, so it flagged the data as untrustworthy rather than treating it as a valid reading.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaInvalid data received from a module

Symptoms you may notice

  • The supplemental restraint system (SRS) warning light is illuminated on the dashboard.
  • The airbag or seatbelt pretensioner system may be disabled as a fail-safe, though the vehicle often drives normally.
  • A message such as 'Service Restraint System' or 'Airbag Fault' may appear in the driver information center.
  • In some vehicles, other modules that share the same CAN bus may log communication codes or show intermittent electrical glitches.
  • Often no symptoms besides the warning light, especially if the fault is intermittent and the sensor data is only occasionally invalid.

Common causes, most likely first

  1. A failing restraints system sensor 'L' that intermittently outputs out-of-range or corrupted data.
  2. Damaged or chafed wiring between the sensor and its control module, causing signal interference or voltage drops.
  3. Corroded or loose electrical connectors at the sensor or at the restraints control module, leading to intermittent data corruption.
  4. A software or calibration issue in the restraints control module that misinterprets valid sensor data as invalid.
  5. Low system voltage or a weak battery that causes modules to reboot or transmit malformed CAN messages.
  6. A faulty restraints control module that cannot properly validate incoming sensor messages.
  7. Aftermarket electronic accessories improperly wired into the CAN bus, introducing noise or invalid data frames.

How to diagnose and fix it

  1. Connect a scan tool and read all stored codes in every module, then record freeze-frame data for U047C to see the conditions when it set.
  2. Inspect the battery, charging system, and ground connections to rule out low voltage as a cause of corrupted CAN messages.
  3. Locate the restraints system sensor 'L' using the vehicle-specific service information, then inspect its connector and wiring for corrosion, chafing, or loose pins.
  4. Perform a wiggle test on the sensor harness while watching live data for the sensor to see if invalid data appears intermittently.
  5. Check for technical service bulletins (TSBs) or software updates for the restraints control module that address false invalid-data codes.
  6. If wiring and voltage are good, substitute a known-good sensor of the same part number and clear the code to see if it returns.
  7. As a last step, diagnose or replace the restraints control module only after confirming the sensor and harness are fault-free.

What most technicians overlook on U047C

  • A weak battery or failing alternator can cause multiple modules to transmit corrupted CAN frames, so always verify charging system health before condemning the sensor.
  • The code names sensor 'L', but on some platforms that label refers to a specific sensor within a multi-sensor restraints array, and swapping sensors without confirming the location wastes time.
  • U047C can be set by a loose aftermarket accessory plugged into the OBD-II port or wired into the CAN bus, so ask about recent electrical additions.
  • The restraints control module may store U047C as a history code long after an intermittent fault has cleared, so clear it and verify it does not return before replacing parts.
  • A sensor that passes a static resistance test can still produce invalid data under vibration or temperature change, making a live-data road test more valuable than a bench check.

Can I keep driving with U047C?

The vehicle is generally safe to drive because the restraints system defaults to a fail-safe mode, but the airbags and pretensioners may not deploy in a crash. Avoid rough roads and electrical system stress until the fault is repaired, and have the system diagnosed promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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