B2651

Code

LAND ROVER B — Body

Body Control Module (BCM) Communication Fault

Brand: LAND ROVER

Type: B — Body

Views: UK: 19 EN: 28 RU: 18

AI status

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Page language: EN

Causes

Open or shorted wiring on data bus (CAN High/Low) between BCM and other modules
Blown fuse or faulty power/ground to the BCM
Poor or corroded connector(s) at the BCM or gateway module
Faulty BCM (internal hardware/software)
Multiple module errors caused by a failing module on the same network
Network termination resistor missing or shorted

Symptoms

No communication with BCM using diagnostic scanner or intermittent connection
Multiple body systems nonfunctional (central locking, interior lights, windows)
Warning messages or lamp(s) illumination related to network or modules
Keyless entry / immobilizer / start/stop anomalies
Intermittent behavior of lights, wipers, HVAC controls or door modules
Vehicle may enter limp or reduced functionality modes

What to check

Read all stored and pending DTCs from BCM and other modules; note freeze-frame and time stamps
Check battery voltage and health; ensure >12V during tests
Inspect fuses and relays supplying BCM and related networks
Visually inspect BCM connector(s) and wiring for corrosion, damage, water ingress or loose pins
Verify solid ground(s) at BCM and nearby chassis grounding points
Attempt to communicate with BCM using OEM scan tool; check for intermittent comms

Signal parameters

CAN idle: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive state)
CAN dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (during data bits)
Differential voltage (CAN_H - CAN_L) should toggle ±2 V during communication
Bus termination: about 60 Ω between CAN_H and CAN_L (two 120 Ω in parallel)
Expected CAN bus speed depends on vehicle (commonly 250 kb/s or 500 kb/s on different networks)
No continuous dominant state or excessive error frames during normal operation

Diagnostic algorithm

Capture all DTCs from BCM and other modules; record time and frequency of B2651 occurrences.
Check battery condition and secure battery terminals; ensure stable supply during tests.
Inspect BCM fuse(s) and supply/ground circuits; repair any open or high-resistance grounds.
With ignition ON, verify scan tool can communicate with BCM; if not, confirm whether other modules on same bus respond.
Visually inspect BCM connector and harness for corrosion, bent pins, water damage; wiggle harness while monitoring communication for intermittent faults.
Check CAN bus physical layer: measure CAN_H and CAN_L at BCM connector and at least one other node. Look for expected idle and dominant voltages.
Check differential voltage and use oscilloscope to examine waveform for noise, reflections, stuck dominant, or missing recessive states.
Measure bus termination resistance (~60 Ω). Disconnect modules as needed to isolate a shorted node.
If a specific module is pulling the bus, disconnect that module and re-check communications to see if B2651 clears.
Inspect and test wiring harness continuity between BCM and gateway/other modules; repair chafed or damaged sections.
If wiring and power/ground are correct and bus signals are healthy, attempt module reprogram/reflash with latest OEM software and clear codes.
If reflash fails or comms remain unreliable, consider replacing the BCM as a last step after confirming harness and other modules are good. Document the steps and test drive to confirm repair.

Likely causes

Intermittent connector corrosion at BCM pin(s) or chassis ground
Damaged CAN bus wiring (pinched, chafed, rodent damage)
Failed BCM after water ingress or shock
Loose or blown 12V supply or battery terminal affecting BCM power
Other module on same CAN network pulling bus dominant (short to ground/12V)
Incorrect or outdated BCM software requiring reflash

Fault status

⚠️ Status

BCM Communication Fault — The Body Control Module failed to communicate properly on the vehicle network. This can be caused by wiring, power/ground, other modules on the CAN bus, or BCM internal failure. Further diagnosis is required to isolate the source.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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