What it means
A control module has stopped receiving expected messages from the left front distance range sensor. The code identifies the communication loss; related distance-sensing functions may be unavailable.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
The left front distance range sensor supplies distance information to vehicle systems that use it for driver assistance. U023D is set when another module stops receiving expected network messages from the left front sensor; it does not identify the right front sensor.
Common causes
Most likely first.
- Loss of power or ground to the sensor
- Open, shorted, or damaged network wiring or connector
- Failed sensor
Symptoms
- Related distance-sensing or driver-assistance functions may be unavailable
- A warning may appear depending on the vehicle
How to diagnose it
- Use a scan tool to record freeze-frame data and check for companion codes that distinguish the left front sensor fault from a shared network or power problem.
- Check live data for the left front distance range sensor and compare its communication status with the right front sensor.
- Inspect the left front sensor face, connector, and accessible wiring for dirt, impact damage, looseness, corrosion, or water intrusion.
- Check the left front sensor’s power and ground against the manufacturer’s wiring information.
- Test the network wiring to the left front sensor for opens or shorts using the manufacturer’s procedure.
- If wiring and supplies are sound, follow the vehicle-specific procedure to confirm whether the left front distance range sensor has failed.
Common fixes
- Clean the left front sensor face if it is obstructed, following vehicle instructions.
- Reconnect or repair a loose or corroded connector at the left front sensor.
- Repair damaged network wiring to the left front sensor.
- Restore the sensor’s power or ground connection.
- Replace the left front distance range sensor if testing confirms it has failed.
Can I keep driving?
Assume distance-sensing assistance that depends on the left front sensor is unavailable, and judge clearance and hazards yourself. Avoid relying on automated distance functions until the fault is repaired.
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.