B1B25

Code

LAND ROVER B — Body

Body Control Module — CAN Bus Communication Fault

Brand: LAND ROVER

Type: B — Body

Views: UK: 16 EN: 30 RU: 16

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Page language: EN

Causes

Open, shorted or corroded CAN H / CAN L wiring or connectors
Poor BCM power or ground connections (low battery voltage, intermittent ground)
Failed BCM CAN transceiver or internal BCM electronics
Missing or failing termination resistor(s) on the CAN bus
Intermittent connection from aftermarket accessories or modules tied into the bus
Other module(s) driving the bus improperly (bus-off condition) or saturating the network

Symptoms

Multiple unrelated warning lamps or messages (e.g., door, lighting, instrument cluster)
Loss of remote locking, interior lights, or other BCM-controlled functions
Intermittent or permanent loss of communication with one or more modules on scan tool
Modules appear to go to sleep and do not wake, or cannot be communicated with
Erratic behavior of electrical systems controlled by BCM

What to check

Connect a capable diagnostic scanner and read all stored and pending DTCs across networks; note module presence and bus-off flags
Check vehicle battery state of charge and measure battery voltage at rest and during cranking
Visually inspect BCM connector, harness and nearby grounds for corrosion, water ingress or damage
Verify fuses and power feeds to BCM and related modules
Measure CAN bus voltages at the BCM connector with key on (see signal parameters)
Measure termination resistance between CAN H and CAN L (expect ~60 ohms if two 120 Ω terminators present)

Signal parameters

Idle (recessive) CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both around mid-supply)
Dominant state example: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V) while transmitting
Typical bus termination resistance ≈ 60 Ω (two 120 Ω terminators in parallel)
Common high-speed CAN bit rates: 500 kbps (vehicle dependent); some networks use 250 kbps or 125 kbps
Excessive noise, missing transitions or one line stuck at 0 V/12 V are indicators of wiring or short

Diagnostic algorithm

Read all network DTCs and record module availability and freeze-frame data. Note whether DTC is current, intermittent or historical.
Check battery voltage and charging system. Low voltage can cause communication errors—restore good battery voltage before further tests.
Inspect BCM and nearby harness/connectors for physical damage, water intrusion, corrosion or loose pins. Repair any damage.
Verify BCM power and ground circuits: measure supply voltages and resistance to ground. Replace blown fuses and repair poor grounds.
With key ON, measure CAN_H and CAN_L at the BCM connector with a multimeter. If levels are grossly out of range, isolate wiring or connectors.
Measure CAN termination resistance between CAN_H and CAN_L with power off; expect ≈60 Ω. If open or very low, locate missing/shorted terminator.
Use an oscilloscope or CAN bus analyzer to view waveforms and error frames. Look for bus-off nodes, dominant stuck levels, or excessive error frames.
Isolate segments: disconnect suspected modules or aftermarket devices one at a time (while observing bus) to find a faulty node causing network problems.
If wiring and external modules check good and diagnostics point to BCM, verify software/calibration and perform BCM reflash or replacement per OEM procedure.
After repairs, clear codes, confirm network stability and operate affected systems to ensure fault does not return.

Likely causes

Loose or corroded BCM connector or pin(s)
Damaged wiring harness in door sills, under dash or near hinge points
Blown fuse for BCM power/ignition feed
Failed CAN transceiver on BCM or another module
Aftermarket alarm/remote start or audio unit improperly connected to CAN

Fault status

⚠️ Status

BCM CAN Bus Communication Fault — the Body Control Module has detected loss or corruption of CAN bus messages to/from other network modules. Check wiring, power/ground, termination and module presence before replacing the BCM.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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B1B25 — Body Control Module — CAN Bus Communication Fault