U02B4 code meaning
Lost Communication With Front Radar Module A
What U02B4 means
At the front, radar modules measure range and speed of the traffic ahead, which adaptive cruise and automatic braking rely on; corner units also watch crossing traffic. U02B4 means module A no longer answers the assistance controller. No manufacturer documents U02B4 publicly, and letters differ by brand: on the 2026 Mercedes-Benz CLA electric (series 174) the invalid-data partner U05B555 shows that front radar A is the outer left unit, read by controller N62/5. GM uses its own code instead: its 2025 tables report a silent long-range radar as U0235 after 0.25 s, classed as emission-neutral Special Type C without lamp, and switch off adaptive cruise. U02B4 should behave alike: assistance messages, no MIL, normal engine operation. After a bumper repair or radar swap, calibration is often required.
U02B4 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.3 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U02B4
- Adaptive cruise and collision warning unavailable
- Driver assistance message in the cluster
Common causes of U02B4
- Most likelyRadar connector behind the bumper not latched, corroded or damaged after a collision
- PossibleSupply, ground or fuse of the radar interrupted
- PossibleRadar module failed
- Less likelyLow battery voltage at start-up
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Front radar module aVehicle bus wiring
What each part of U02B4 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B4 | The exact fault in that area. |
What to do next
- Note U02B4 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U02B4
What does U02B4 mean?
U02B4 means "Lost Communication With Front Radar Module A". At the front, radar modules measure range and speed of the traffic ahead, which adaptive cruise and automatic braking rely on; corner units also watch crossing traffic. It is a generic code, so it means the same on every make.
Is it safe to drive with U02B4?
U02B4 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U02B4 fail an emissions test?
U02B4 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U02B4 to fix?
Difficulty: hard. A typical repair takes 0.3 to 3 hours of work. This is a job for a workshop.
Will U02B4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.