B10DC

Code

Generic B — Body

Body Control Module CAN Bus Communication Timeout

Brand: Generic

Type: B — Body

Views: UK: 9 EN: 13 RU: 8

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Page language: EN

Causes

Faulty BCM (internal failure or software crash)
Open/shorted CAN H or CAN L wiring or poor connector/terminal contact
Missing or incorrect termination resistor(s) on CAN bus
Power or ground problem to the BCM (low battery, blown fuse, poor ground)
Another module on the network is driving the bus (bus-off) or flooding the bus with errors
Module in sleep/standby not waking or incorrect wake signal

Symptoms

BCM appears unresponsive or intermittent (doors, interior lights, wipers, locks not working)
Multiple communication-related DTCs present (other modules show loss-of-communication codes)
No BCM messages visible on the CAN bus with a scan tool or oscilloscope
Certain modules report ‘module not present’ or behave incorrectly
Vehicle may fail to wake or modules may go to bus-off state

What to check

Verify battery voltage is stable (12.4–13.0 V with key off, ~13.5–14.8 V with engine running) and battery terminals are clean and tight
Scan the network with a professional scan tool: read all stored/active codes and check which modules are present
Check BCM power and ground circuits and all related fuses and relays
Visually inspect BCM connector and CAN wiring for damage, corrosion, bent pins or water intrusion
Measure CAN bus voltages at BCM connector: CAN_H and CAN_L idle voltages and termination resistance across CAN_H–CAN_L
Use an oscilloscope or CAN bus monitor to verify bus activity, message timing, and presence of error frames

Signal parameters

CAN_H idle ≈ 2.5 V (typical)
CAN_L idle ≈ 2.5 V (typical)
Recessive state: CAN_H ≈ CAN_L (small differential)
Dominant state differential ≈ 1.5–2.5 V (CAN_H rises ~3.5 V, CAN_L falls ~1.5 V)
Termination resistance across CAN_H–CAN_L ≈ 60 Ω (two 120 Ω terminations in parallel)
Common bus speeds: 125 kbps, 250 kbps, 500 kbps (confirm vehicle-specific baud rate)

Diagnostic algorithm

Record freeze-frame data and note any other communication or module-not-present codes with a scan tool.
Verify battery condition and BCM power/ground: check relevant fuses, relays and harness power feeds.
Visually inspect BCM connector and CAN wiring for damage, corrosion, chafing or disconnected splices; repair as needed.
With key off, measure DC voltage at BCM power and grounds; confirm within spec.
Check passive CAN layer: measure resistance across CAN_H–CAN_L at vehicle harness—expect ≈60 Ω. If open or very low, follow wiring to find break or short.
Use an oscilloscope or CAN interface tool to monitor CAN_H and CAN_L at the BCM with ignition in run and accessories active. Look for expected idle voltages, message frames, and absence/presence of error frames or continuous dominant state.
If bus is silent at BCM but other modules present elsewhere, isolate harness sections (disconnect connectors) to locate the open/shorted segment.
If a single module is flooding/errors on the bus, disconnect suspected modules one at a time to see if network recovers.
Check for aftermarket devices and disconnect them to rule out interference.
If wiring and bus behavior are good and BCM still times out, perform BCM software/firmware reflash if available from manufacturer.
Replace BCM only after verifying physical layer, power/ground, terminations and confirming replacement is required; program/configure new BCM per manufacturer procedures.

Likely causes

Connector corrosion or loose pins at BCM or splice points
Broken or shorted CAN H/L wiring near BCM (most common)
Missing/failed termination (open 120 Ω) or additional improper termination
BCM power/ground fault preventing normal operation
Faulty BCM electronics or failed firmware

Fault status

⚠️ Status

Body Control Module CAN Bus Communication Timeout — BCM did not receive required CAN messages within the expected timeout period. Check power/ground, wiring, termination and bus activity before replacing module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-4 hours