B298E

Code

Generic B — Body

Body Control Module Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 3 EN: 13 RU: 11

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Page language: EN

Causes

Faulty BCM (internal failure or software error)
Open, short or high resistance in CAN/wiring harness between BCM and network
Poor power supply or ground to the BCM (low battery, corroded ground)
Faulty connector or pin damage at BCM or intermediate junctions
Bus termination fault (missing or incorrect resistor) or short to battery/ground on CAN_H or CAN_L
Intermittent connection caused by chafed wiring, water intrusion or corrosion

Symptoms

Warning lights on instrument cluster (communication warnings)
Loss or intermittent operation of body functions (locks, lighting, wipers, HVAC, immobilizer)
No response to remote/keyless entry or intermittent remote operation
Multiple module communication errors present on a scan tool
Some modules report ‘‘no communication’’ or go bus-off

What to check

Retrieve freeze frame and full communication list with a scan tool; note time/states when fault logged
Check battery voltage at rest and cranking; ensure proper battery state (12.4–12.8V nominal at rest)
Verify BCM key power and ground pins for good contact and
Visually inspect BCM connectors and harness for corrosion, bent pins, water intrusion and damage
Check CAN bus physical condition and routing for chafe points or recent repairs
Check for related network U-codes (U0100, U0140, etc.) to find affected segments

Signal parameters

CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V, differential ≈ 0 V
CAN bus dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V, differential ≈ 2 V
Expected CAN bus resistance between H and L (ignition off): ≈ 60 Ω (two 120 Ω terminators in parallel)
No continuous short to battery or ground on CAN lines (measure resistance to battery and ground)

Diagnostic algorithm

Safety first: follow vehicle-specific service manual and disconnect battery per procedure when required; use ESD precautions when handling modules.
Connect a capable scan tool and record active/stored DTCs and live network module list. Note which modules are missing or reporting errors.
Attempt to recreate the fault by cycling ignition and operating affected circuits; watch live data and module presence.
Check BCM power and ground: verify voltages at connector with ignition on/off and measure ground resistance to chassis.
Visually inspect connectors and harness; repair any corrosion, bent pins or damaged insulation. Re-seat connectors and apply dielectric grease where appropriate.
Measure CAN_H and CAN_L voltages at the BCM connector with key on. Compare to expected signal_params. If bus is silent or stuck, look for shorts/open circuits.
Measure resistance between CAN_H and CAN_L with key off; confirm ~60 Ω. If not, isolate segments by disconnecting harnesses/modules to find section causing mismatch.
Wiggle-test harness and connectors while monitoring bus and for intermittent errors to locate broken wires.
If wiring and power/ground are good, update BCM software/calibration per OEM procedure, then clear codes and retest.
If all wiring, power, ground and bus termination verified and code persists, consider swapping in a known-good BCM or bench-testing BCM per manufacturer guidelines before replacement.
After repair, clear DTCs and verify vehicle functions and network stability over a road test or extended cycle.

Likely causes

Faulty or loose BCM ground or power supply
Damaged or corroded connector pins at the BCM
Short or open on CAN_H or CAN_L wiring near BCM or junctions
Bus termination resistor missing or open
Faulty BCM after wiring and power/ground verified

Fault status

⚠️ Status

Body Control Module communication fault stored—BCM not responding properly on vehicle network or network errors detected. Verify wiring, power/ground, and other modules before replacement.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours