B2A53

Code

Generic B — Body

Body Control Module — CAN Bus Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 14 RU: 16

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Page language: EN

Open or short in CAN_H or CAN_L wiring
Damaged, corroded, or loose connector at BCM or other CAN nodes
Failed BCM CAN transceiver or internal BCM fault
Missing or incorrect termination resistor(s) on the CAN bus
Low battery voltage, poor power/ground to BCM, or intermittent supply
Faulty or misconfigured module elsewhere on the CAN bus causing bus-off or excessive error frames

Warning lamp(s) illuminated on dash (CAN/BCM warnings)
Loss or intermittent operation of body systems controlled by BCM (lights, door locks, windows, wipers, etc.)
Stored multiple network/communication trouble codes
Reduced or no CAN traffic seen by diagnostic scanner on BCM network
Intermittent or persistent infotainment/telematics or instrument cluster failures

Read all stored and pending DTCs on all modules with a capable scan tool; note freeze frame and occurrence counts
Check BCM power and ground voltages at the connector with key ON; verify battery present and stable
Visually inspect BCM connector and nearby harness for corrosion, damage, or water intrusion
With key ON, use scan tool to view CAN bus message list and message frequency; note missing modules
Measure CAN bus idle voltages: CAN_H and CAN_L at BCM connector (nominal ~2.5 V each)
Measure resistance between CAN_H and CAN_L with ignition OFF (expected ~60 ohms for properly terminated single-bus systems; two 120Ω terminators in parallel = 60Ω)

CAN_H idle ≈ 2.5 V (range ~2.0–3.0 V depending on network)
CAN_L idle ≈ 2.5 V (range ~2.0–3.0 V)
Dominant state typical differential ≈ 1.5–3.0 V (CAN_H rises ~+1.0 V, CAN_L falls ~−1.0 V)
Recessive state differential ≈ 0 V (both near 2.5 V)
Typical bus speeds: 125 kb/s, 250 kb/s, 500 kb/s (verify vehicle-specific rate)
Termination expected: two 120 Ω resistors (one at each end) => measured ~60 Ω across CAN_H–CAN_L with network intact

Connect a capable scan tool and read all modules; record all communication errors and module absence
Verify and record BCM supply and ground voltages with key ON; repair any low/erratic supply or poor ground before further tests
Visually inspect BCM connector and nearby harness for damage, corrosion, water; repair/clean as needed
Measure CAN_H and CAN_L idle voltages at BCM connector; if voltages are out of nominal range, trace wiring and check transceiver power pins
Measure resistance between CAN_H and CAN_L with ignition OFF; if not ~60 Ω, check for missing or damaged terminators and inspect harness for shorts/opens
Use an oscilloscope on CAN_H and CAN_L with the network active to observe waveform shape, amplitude, and noise. Look for stuck dominant, excessive noise, or missing edges
If a bad waveform or error frame source is suspected, isolate by disconnecting downstream modules one at a time (or sections of the bus) while observing bus behavior to find the faulty node
If wiring, termination, and other modules check good and BCM is only suspect, verify BCM software level and reflash/upgrade if available, then replace BCM if internal transceiver or internal faults are confirmed
After repairs or module replacement, clear codes, restore any module coding/parametrization, and perform full network scan and road test to confirm no recurrence