B134D

Code

LAND ROVER B — Body

Body Control Module (BCM) — internal communication fault

Brand: LAND ROVER

Type: B — Body

Views: UK: 21 EN: 25 RU: 21

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Page language: EN

Causes

Faulty BCM hardware or internal electronics
Corrupted BCM software or firmware
Low or unstable vehicle battery voltage or poor ground
Damaged or corroded BCM connectors or pins
CAN/LIN bus wiring faults, shorts or high resistance
Water intrusion or physical damage to BCM housing

Symptoms

Multiple intermittent or permanent body system faults (locks, lights, windows, interior lighting)
One or more modules show 'no communication' or related U-codes on a scan tool
Warning messages or lamp illumination on instrument cluster
Remote keyless entry, alarm or immobilizer issues
Failed or non-functional comfort features (wipers, climate vents, mirrors)

What to check

Connect a capable diagnostic scanner and read all stored and pending codes from BCM and other modules; record freeze frame/live data
Verify battery state-of-charge and charging system; confirm stable 12V with engine off and during cranking
Inspect BCM connectors and harness for corrosion, bent pins, water ingress and secure mating
Check fuses and relays related to BCM power/ignition circuits
Verify vehicle ground points and measure continuity between BCM ground and chassis
Measure CAN/LIN bus voltages at the BCM connector with key on (see signal parameters)

Signal parameters

Battery supply to BCM: ~12 V (key off), ~11–14.5 V (during cranking/charging)
Ground continuity: near 0 ohms between BCM ground terminal and chassis
CAN bus idle voltages (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V
CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (approx. ±2 V differential)
Termination resistance: ≈ 60 ohms measured across CAN_H and CAN_L at the harness

Diagnostic algorithm

Use a manufacturer-level scan tool to read all codes from BCM and all network modules; save reports and note time stamps and freeze-frame data.
Verify vehicle battery voltage and health; recharge or support with a stable power supply during testing to avoid false results.
Visually inspect the BCM and nearby harness for signs of water ingress, corrosion, heat damage or physical impact; secure and reseat connectors.
Check fuses and relays supplying the BCM; replace any blown items and re-test communications.
With key in ON, check CAN/LIN voltages and termination resistance at the BCM connector; look for stalled or dominant nodes and wiring shorts.
Use an oscilloscope or CAN bus analyzer if available to capture traffic and identify CRC errors, bus errors or repeated reboots of the BCM.
If other modules report communication loss to the BCM, isolate by disconnecting suspected nodes or segments and retesting until the fault narrows to wiring or a single module.
Attempt a power-cycle and then use the dealer tool to attempt a BCM reflash or software integrity check; apply any available software updates.
If diagnostics indicate internal BCM failure (persistent internal communication fault, no successful reflash, internal hardware errors), prepare for module replacement and required programming/coding.
After repair or replacement, reprogram/configure BCM to vehicle specification, clear codes, and perform a full system verification and road test to confirm the issue is resolved.

Likely causes

Failed BCM electronics (age, heat or moisture related)
Battery/charging system problem causing communication errors
Poor connector/terminal contacts (corrosion or bent pins)
Network wiring fault (broken shield, short to supply or ground)
Software/firmware corruption or missing calibration after service

Fault status

⚠️ Status

BCM internal communication fault — module reports an internal communications failure; may be intermittent or persistent and can affect multiple body systems.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5 - 4.0 hours

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