U2023

Code

LAND ROVER U — Network/User

Failure received from the external node

Brand: LAND ROVER

Type: U — Network/User

Views: UK: 22 EN: 39 RU: 24

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Page language: EN

Causes

Fault reported by an external control module (node)
Intermittent or failed connector at the external module
Open/short/high resistance in CAN/LIN wiring between gateway and node
Poor power or ground at the external node
Module software mismatch or corrupted calibration
Bus termination or wiring short (CAN high/low shorted to each other, battery, or ground)

Symptoms

Warning message(s) for the affected system(s) on dash or information display
Loss or degradation of function controlled by the external node (e.g., ADAS, ABS, HVAC, infotainment)
Multiple network-related DTCs present on scan tool
Module not responding or showing as 'not present' in diagnostics
Intermittent faults that clear after power cycle or return after driving

What to check

Read and record all DTCs and freeze frame data from all modules (note timestamps)
Check battery voltage and charging system health (stable supply during diagnosis)
Visually inspect connectors and wiring at the indicated external module and along the harness for damage, corrosion, or pins pushed out
Verify fuses and local power/ground at the external node
Scan for other network U-codes (bus-off, lost communication) to identify affected bus or gateway
Check CAN/LIN termination resistors and measure bus idle voltages with a DMM

Signal parameters

Typical CAN recessive idle voltages: CANH ≈ 2.5 V, CANL ≈ 2.5 V
CAN dominant state: CANH ≈ 3.5–4.5 V, CANL ≈ 0.5–1.5 V
Typical CAN termination: two 120 Ω resistors in parallel (≈60 Ω across CANH–CANL)
Common bus speeds: 500 kbps (high speed), 250 kbps or 125 kbps depending on subsystem; confirm vehicle-specific baud rate
Message behavior to check: expected periodic IDs from external node, message frequency, and timeouts (missing message thresholds)

Diagnostic algorithm

Record all network-related DTCs from every module and confirm occurrence conditions/timestamps. 2) Reproduce the fault if possible (same driving condition, ignition cycle). 3) Inspect power, ground, and fuses for the external node; repair any faults. 4) Visually inspect and secure the node connector and harness; repair damaged wiring or corroded terminals. 5) Check CAN/LIN physical layer: measure idle voltages, check termination resistance (~60 Ω across CANH–CANL). 6) Use a scope/CAN tool to capture traffic: verify the external node’s message IDs are present and check for error frames or bus-off. 7) If node messages are absent and wiring is OK, attempt reprogramming/reflashing the node software per manufacturer procedures. 8) If possible, swap with a known-good module or attach a bench-tested module to confirm node failure. 9) Clear DTCs and re-test to verify repair; if intermittent, perform wiggle tests and extended road test. 10) If diagnostics point to gateway or multiple bus errors, follow manufacturer gateway diagnostics and escalate to module replacement only after isolating wiring and power/ground issues.

Likely causes

Failed external module (hardware or internal firmware)
Damaged/contaminated connector at the module
Local power/ground fault at the external node (blown fuse, poor earth)
CAN bus wiring short or high resistance connection between modules
Incorrect or incomplete software/ECU flash causing the node to enter fault state

Fault status

⚠️ Status

Communication fault — external node reported failure

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5 to 4.0 hours

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