What it means
A receiving module detected implausible data from the front distance range sensor (single or center-mounted long-range radar/lidar). Distance/closing-speed values fail plausibility checks and are rejected by ACC/AEB.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The cruise control front distance range sensor measures the road ahead and provides distance and closing-speed data for adaptive cruise control and, where fitted, emergency braking. U0433 sets when a receiving module rejects the sensor's reported data as implausible. A sensor fault, incompatible replacement software, or incorrect network routing can make those driver-assistance functions unavailable.
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 U0433, related radar or driver-assistance codes, and freeze-frame data to identify which module rejected the sensor messages.
- Check live distance and closing-speed data while stationary and during a safe controlled check, looking for missing or implausible readings.
- Inspect the front distance sensor's mounting, cover, connector, and wiring for obstruction, damage, looseness, or evidence of misalignment.
- Check for recent sensor or module replacement and verify the software and configuration match the vehicle.
- Test sensor power, ground, communication wiring, and gateway routing to the manufacturer's specification before condemning the sensor.
Common fixes
- Remove dirt or an obstruction from the sensor cover and restore a secure mounting.
- Repair damaged wiring or a loose, corroded sensor connector.
- Correct incompatible software or module configuration after replacement.
- Repair a confirmed gateway or network communication fault.
- Replace or calibrate the front distance sensor only if testing confirms a sensor fault and the manufacturer requires it.
Can I keep driving?
Adaptive cruise control and automatic emergency braking may be unavailable or limited; do not rely on them to maintain distance or prevent a collision. Drive with extra following distance and use normal braking.
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.