B11C5

Code

Generic B — Body

Body Control Module CAN Communication Fault with Door Module

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 16 RU: 7

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open, short or high-resistance wiring on CAN bus between BCM and door module
Corroded or loose connector pins at BCM or door module
Missing or incorrect CAN bus termination resistor(s)
Loss of power or ground to the door module or BCM
Faulty door module or BCM (internal communication hardware or firmware)
Aftermarket device or recent wiring modification interfering with the bus

Symptoms

Door locks/unlocks unresponsive or intermittent
Power window, mirror, or interior light functions on affected door fail
Door ajar or keyless entry warnings/messages displayed
Related control modules show communication errors or reduced functionality
Stored communication-related DTCs and possible amber warning on dash

What to check

Scan for DTCs and log related historical codes from all networked modules
Visually inspect connectors and wiring at BCM, affected door module(s) and common splice points
Check fuses and relay feeding door module power circuits
Measure and compare supply voltage and ground at the door module connector (key on)
Measure CAN_H and CAN_L voltages at BCM and door module connectors
Measure termination resistance between CAN_H and CAN_L with ignition off

Signal parameters

CAN bus idle (recessive) common mode: ~2.5 V on both CAN_H and CAN_L
CAN bus dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 1.5–2.5 V)
Termination resistance across CAN_H–CAN_L ≈ 60 Ω (two 120 Ω terminators in parallel)
Typical CAN bus speeds: 125 kb/s, 250 kb/s, 500 kb/s or 1 Mb/s (vehicle-specific)
Module supply voltage expected ~11–14.5 V; ground continuity

Diagnostic algorithm

Record freeze-frame data and all related communication codes from scan tool
Visually inspect wiring and connectors at the affected door(s) and BCM; repair any obvious damage or corrosion
Check fuses/relays for the door module power circuit; measure supply voltage and ground at the door module connector (key on)
With ignition on, measure CAN_H and CAN_L at the BCM and at the door module connector: confirm recessive common mode ≈2.5 V and expected dominant levels during activity
With ignition off, measure resistance across CAN_H–CAN_L at two nodes to confirm ~60 Ω termination; inspect for extra stubs or un-terminated branches
If physical layer looks good, use a scope to observe CAN waveforms while exercising door functions (unlock/lock, window) to detect reflections, noise or bus-off conditions
Disconnect aftermarket devices and isolate the circuit by unplugging suspected door module(s) to see if bus recovers; test communications with only BCM and one door module connected
If wiring/power/termination are good, try programming/reflashing or resetting the door module and BCM per manufacturer procedures
If module remains unresponsive after validating wiring, power and software, consider replacing the faulty module (replace door module first if isolated) and then clear codes and retest

Likely causes

Damaged/shorted CAN wiring or pin corrosion at door harness
Power/ground fault to the door module (blown fuse, poor ground)
Missing/bad termination resistor or stub causing reflections
Door module internal failure or bus-off condition
Recent module replacement not programmed or incompatible software

Fault status

⚠️ Status

Body Control Module - CAN communication fault with door module. Indicates loss or corruption of messages between BCM and door module due to wiring, power/ground, termination, or module fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours