U04BB

Code

Generic U — Network/User

Invalid Data Received from Switch Input Module “B”

Brand: Generic

Type: U — Network/User

Views: UK: 29 EN: 35 RU: 25

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Corroded, loose or damaged connector at Switch Input Module B
Faulty Switch Input Module B hardware or internal software fault
Network wiring fault (CAN/LIN) between module B and main gateway/ECU
Bus termination or grounding issues causing corrupted messages
Software/configuration mismatch after ECU/module replacement or update
Interference from aftermarket electronics or short to battery/ground

Symptoms

Malfunction or intermittent operation of switches assigned to Module B (e.g., door, steering, or console switches)
Warning or communication DTCs present on scan tool
Loss of related functions (lighting, windows, steering wheel controls, etc.)
Intermittent or erratic vehicle behavior tied to switch inputs
Multiple network-related faults when bus is heavily loaded

What to check

Read all U-codes and related P/C/B codes with a capable scan tool and note freeze frame or active status
Check for other modules reporting CAN/LIN errors or lost communication
Visually inspect connectors and wiring to Switch Input Module B for corrosion, bent pins or water ingress
Measure battery voltage and check module supply/ground at the connector
Use an oscilloscope or CAN/LIN monitor to capture bus traffic and look for malformed frames, incorrect IDs, or bus errors
Measure CAN_H and CAN_L voltages with key on/engine off; check termination resistance across bus (~60 ohm typical)

Signal parameters

Typical CAN idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V; dominant state CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (varies by vehicle)
Common CAN data rates: 125 kb/s, 250 kb/s, 500 kb/s; confirm vehicle-specific bitrate with scan tool
LIN bus (if used) is single-wire, idle ~battery voltage through pull-up, frames use timed breaks and checksums
Message frequency: switch module messages often repeat at 10–100 ms when active; look for missing or corrupted payloads
Watch for CRC/checksum failures or unexpected message IDs/lengths in captured frames

Diagnostic algorithm

Connect a full-function scan tool. Record all U-codes and note whether U04BB is active or stored.
Use a bus monitor or oscilloscope to observe traffic from Switch Input Module B. Confirm expected message ID, length and update rate; note any malformed frames or CRC errors.
With ignition off, perform a visual inspection of the module connector and associated wiring harness for damage, corrosion or water contamination. Repair any physical damage.
With ignition on, verify module power and ground at the connector pins using a multimeter. Compare to vehicle specifications.
Check CAN/LIN wiring continuity and shorts: measure resistance between CAN_H and CAN_L (should be ~60 ohm across the two termination resistors) and to chassis/power for shorts.
If bus errors or corrupted frames are found, isolate by disconnecting the module while monitoring the bus to see if errors clear. Reconnect to confirm fault follows module or wiring.
If wiring and supply are good but invalid data persists, check software calibration/part numbers and update or reflash module firmware per manufacturer procedures.
Swap with a known-good module (if available and allowed) or replace the module only after wiring and network integrity are confirmed.
After repair, clear codes and verify operation through full re-test and road-test to ensure no recurrence.

Likely causes

Open or high-resistance connection at the module connector
CAN or LIN bus shorted, intermittent or missing termination
Module firmware mismatch or corrupted calibration data
Module internal failure causing bad checksums/frames

Fault status

⚠️ Status

Invalid or malformed data received from Switch Input Module "B". The receiving control unit detected message format, checksum, ID, or timing errors and flagged the communication as invalid. Issue may be wiring, module power/ground, bus termination, software mismatch, or a faulty module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours