What it means
A receiving module detected implausible data from the front-left distance range sensor (corner radar). Distance/azimuth values fail plausibility checks and are rejected by ADAS functions.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The front-left corner radar reports its detected distance and angle over the vehicle network for cruise control and other driver-assistance functions. A receiving module sets U043B when that left-side radar data fails its plausibility checks and is rejected; the code does not by itself prove the radar has stopped communicating.
Common causes
Most likely first.
- Module internal fault or sensor input drift
- Software version mismatch after replacement
- Gateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules and save freeze-frame data and communication codes to identify which module rejected the front-left radar data and when the fault occurred.
- Check live data for the front-left radar's reported distance and angle, and compare them with the front-right radar and the visible road scene.
- Inspect the front-left radar's mounting, cover, connector, and nearby wiring for damage, contamination, misalignment, or signs of recent repair.
- Check the network for related communication or gateway faults and inspect the relevant connectors and wiring for looseness, corrosion, or damage.
- If the radar or a related module was replaced, verify compatible software and calibration, then follow the vehicle's service procedure to test the radar and receiving module.
Common fixes
- Clean the front-left radar cover and remove anything obstructing it.
- Repair a damaged or loose front-left radar connector or harness.
- Correct front-left radar mounting or calibration if it is misaligned.
- Update or configure replacement radar, gateway, or receiving-module software as specified for the vehicle.
- Replace the front-left radar or repair the receiving module only after testing confirms the fault.
Can I keep driving?
If the warning is limited to driver-assistance features, drive manually and leave adaptive cruise or other affected assistance functions off; they may not respond reliably. If other warnings affect steering, braking, or vehicle control, stop in a safe place and arrange assistance.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.