B111F

Code

LAND ROVER B — Body

Body Control Module — CAN Bus Communication Fault

Brand: LAND ROVER

Type: B — Body

Views: UK: 15 EN: 25 RU: 16

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Page language: EN

Causes

Poor BCM power or ground (low battery, blown fuse, corroded ground)
Damaged or corroded BCM connector pins or wiring harness
Short or open in CAN_H or CAN_L wiring
Missing or incorrect CAN bus termination (open/shorted resistors)
Faulty BCM (internal failure)
Faulty gateway/module elsewhere on the CAN bus

Symptoms

CAN-related module warnings (multiple modules reporting communication errors)
Loss or intermittent operation of body functions (locks, lights, windows, wipers)
Instrument cluster warnings or message such as 'CAN BUS FAULT'
Inability of diagnostic tool to communicate with BCM or other modules
Erratic behaviour of multiple unrelated systems

What to check

Connect a diagnostic scan tool and record all stored and pending codes and freeze-frame data
Check battery voltage (should be within specified range, typically ~12.4–12.8 V at rest) and charging system health
Visually inspect BCM connector and nearby harness for corrosion, bent pins, water ingress, rodent damage or chafing
Check fuses and power feeds to the BCM and related modules
Using the scan tool, list which modules are present/absent on the CAN bus
Measure resistance across CAN_H and CAN_L with ignition off — expected ~60 Ω (two 120 Ω terminators in parallel)

Signal parameters

Idle (recessive) node voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (with respect to vehicle ground)
Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Nominal differential voltage when active: ≈ 1.5–2.5 V
Bus termination: ≈ 60 Ω measured across CAN_H and CAN_L (two 120 Ω terminators in parallel)
Short-to-ground or short-to-Vb on a line will pull voltage toward 0 V or battery voltage respectively and disrupt differential

Diagnostic algorithm

Read and record all DTCs and freeze-frame data with a capable scan tool; note time stamps and related codes.
Verify battery state of charge and charging system; recharge if low and retest codes after power normalization.
Visually inspect BCM connector, pins and chassis grounds; repair any corrosion, bent pins or loose grounds.
Confirm BCM supply voltages and ground presence at the BCM connector (VBATT, ignition feed, ground).
Using a meter/oscilloscope, measure CAN_H and CAN_L voltages with ignition ON (engine off) and verify recessive and dominant levels and differential; compare to signal parameters.
Measure DC resistance across CAN_H and CAN_L with ignition off — expect ~60 Ω; if open or much higher, trace harness for open/short.
If the bus is shorted or stuck dominant, isolate sections by disconnecting devices/modules one at a time (or disconnect connectors at logical splice points) while monitoring the bus to find the offending node.
Perform a wiggle/drive test with monitoring to find intermittent wiring faults; repair damaged wiring or connectors.
If no wiring/connector fault is found and power/grounds are correct, verify software/calibration — check for required BCM software updates or reflash procedure per manufacturer service information.
If BCM is confirmed faulty after isolating the network and verifying other modules, replace BCM and perform required programming/coding; clear codes and verify network operation.
After repair re-scan and perform a road test to ensure fault does not return.

Likely causes

Loose or corroded BCM connector
Short to battery or ground on CAN_H or CAN_L
Open or high-resistance CAN line (broken wire or connector)
Incorrect/missing termination resistors (expected ~60 Ω across bus)
Other module pulling the bus dominant or holding a line low/high

Fault status

⚠️ Status

Body Control Module reports CAN bus communication fault — BCM not receiving/transmitting expected CAN messages. Fault logged when communication timeout, bus fault, or invalid CAN signals detected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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