U02B5

Code

Generic U — Network/User

Lost Communication With Front Radar Module B

Brand: Generic

Type: U — Network/User

Views: UK: 23 EN: 34 RU: 25

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Front radar module B failure (internal electronics/software)
Open, shorted, or intermittent wiring or connector to the radar module
Loss of module power (fused feed, ignition feed, or battery supply)
Bad ground at the radar module or chassis ground
Faulty CAN/LIN/ethernet transceiver or bus device
Missing or improper network termination

Symptoms

Radar system warning lamp or message in driver information display
Adaptive cruise control, automatic emergency braking, or collision mitigation disabled
No radar targets or intermittent target detection in diagnostic tool
Related vehicle functions degraded or unavailable
Stored U02B5 (and possibly related U-codes) in module memory

What to check

Read all stored codes and freeze frame data from all modules; note accompanying U- or B-codes
Check for other modules reporting lost communication on the same network
Verify battery voltage at key on and cranking (12.0–14.5 V typical)
Visually inspect the radar B connector, wiring harness and nearby harnesses for damage or corrosion
Check power and ground pins at the radar module connector for correct voltage and resistance to chassis ground
Scan the vehicle bus with a capable scan tool to see if the radar B node is present and if messages/heartbeat appear

Signal parameters

Typical CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (differential ≈ 0 V); dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (diff ≈ 2.0 V)
Typical bus termination: ≈ 60 Ω measured end-to-end between CAN_H and CAN_L (two 120 Ω terminators in parallel)
Common bus speeds: 500 kb/s (some systems 250 kb/s or 125 kb/s) — verify vehicle-specific rate
Radar module heartbeat/messages: usually a 1 Hz alive/heartbeat and higher-rate object/track messages (object list 5–20 Hz) depending on OEM
Module supply: nominal vehicle battery (≈ 12 V); switched/ignition feed present with key on

Diagnostic algorithm

Retrieve codes from all modules and document occurrences and freeze frame. Clear codes and attempt to reproduce to confirm persistent condition.
Verify vehicle battery voltage and charging system condition to rule out low-voltage related communication failures.
Inspect the front radar B connector and harness for corrosion, loose pins, bent terminals, water intrusion, or recent repair/impact damage.
With a scan tool, check whether the radar B module responds to diagnostic requests or appears on the network. Note message IDs and frequency if visible.
Backprobe the radar module connector: verify constant/switched power, ignition feed (if applicable), and good chassis ground. Repair any power/ground faults before continuing.
Check CAN (or vehicle network) integrity: measure CAN_H and CAN_L idle voltages, check for expected differential on dominant transitions, and verify termination resistance (~60 Ω).
If CAN bus shows no activity for that node, inspect wiring continuity between module and the nearest gateway/module; look for opens or shorts to battery/chassis.
Disconnect the radar B module and observe the bus — in some designs removing a failed module can restore bus communications. If bus restores, suspect the module.
If wiring/power/ground are good and the module does not respond, confirm software/calibration and VIN programming status. Reflash or reprogram per OEM service procedure if required.
Replace the radar module only after confirming the failure is internal or module is non-responsive and retest system operation and communication.
After repair, clear codes and road-test to verify no recurrence. Document any intermittent conditions and monitor related systems.

Likely causes

Corroded or loose connector at the radar module
Damaged CAN high/low wires (pinched, chafed, short to ground or battery)
Blown fuse or switched power feed loss to the radar module
Failed radar module transceiver or internal fault
Aftermarket device or recent repair left the bus un-terminated or miswired

Fault status

⚠️ Status

Control module reports loss of communication with Front Radar Module B — expected messages/heartbeat not received. Radar‑dependent safety features may be disabled.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours