U0001

Code

LAND ROVER U — Network/User

CAN bus communication of high speed

Brand: LAND ROVER

Type: U — Network/User

Views: UK: 36 EN: 57 RU: 103

AI status

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Page language: EN

Causes

Open or short in HS-CAN wiring (CAN_H or CAN_L)
Poor or intermittent ground or battery supply to one or more modules
Damaged or corroded connectors or pins in the CAN bus network
Missing or incorrect termination resistor(s) (open or shorted 120 Ω terminators)
Faulty control module (bus transceiver failure)
Aftermarket accessories or modules interfering with the bus

Symptoms

Multiple warning lights or ECUs reporting loss of communication
Intermittent or complete loss of functions controlled by modules on the HS-CAN bus (e.g., engine, ABS, transmission, instrument cluster)
Engine may crank but not start or run poorly if ECM messages absent
Diagnostic scan tool shows no live data from one or more modules
Erratic messages on scan tool or CAN traffic analyzer (bus errors, repeated reboots)

What to check

Read all stored and pending U-codes and related module codes; note freeze frame and occurrence pattern
Check vehicle battery voltage and charge (13.0–14.8 V typical when running)
Visual inspection of CAN wiring, connectors, and junction boxes for damage, corrosion or water
Inspect termination resistors across CAN_H and CAN_L at both ends of the HS-CAN bus (expected ~60 Ω total, two 120 Ω in parallel)
Verify power and ground circuits to gateway, BCM and modules on the HS-CAN network
Disconnect aftermarket devices or recently serviced modules and re-test

Signal parameters

High-speed CAN nominal bit rates commonly 250 kb/s or 500 kb/s (verify vehicle-specific rate)
Recessive state: CAN_H ≈ CAN_L ≈ 2.5 V (no differential)
Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Termination: 120 Ω resistors at each end of the bus (parallel ≈ 60 Ω measured across CAN_H and CAN_L)
Idle bus shows low CAN traffic and stable recessive voltages; frequent bit errors or constant dominant level indicate fault

Diagnostic algorithm

Capture all U-codes and related module codes with a diagnostic scanner; record conditions (key on, engine running).
Check battery voltage and charging system; repair low supply issues before network diagnostics.
Visually inspect CAN wiring harness, connectors, grounding points and modules for damage or corrosion; repair as needed.
Measure DC voltages at CAN_H and CAN_L at a convenient connector with key ON, engine OFF: expect ~2.5 V each (recessive).
Measure resistance across CAN_H and CAN_L with power off; expect roughly 60 Ω (two 120 Ω terminators in parallel).
Use an oscilloscope or CAN bus analyzer to observe waveform quality and error frames while the network is active; look for constant dominant, excessive collisions, reflections or noise.
Isolate sections of the bus: disconnect non-essential modules or unpin suspected connectors and re-check the bus to see if the condition clears.
Replace or repair damaged wiring, connectors, or termination resistors. If bus still faulty, swap or bench-test suspected module transceivers per manufacturer procedure.
After repairs, clear codes and perform a road test or extended network scan to confirm the fault does not reoccur.
If intermittent, perform wiggle testing of harnesses while monitoring bus with analyzer to reproduce the fault.

Likely causes

Broken or chafed CAN harness at a routing point or behind a connector
Faulty module transceiver (often a single module causing bus error)
Open/shorted termination (missing 120 Ω resistor or short to voltage/ground)
Corroded connector at gateway/module (poor signal continuity)
Low battery voltage or poor ground affecting module operation

Fault status

⚠️ Status

High-speed CAN communication error: network messages missing or invalid. Indicates impaired communication on the vehicle HS-CAN bus; may impact multiple vehicle systems until resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.5 hours

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U0001 — CAN bus communication of high speed