B026A

Code

Generic B — Body

Body Control Module: Missing CAN Message from Door Module

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 22 RU: 12

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Page language: EN

Scan for active and history DTCs on BCM and door module; record freeze frame
Verify vehicle battery voltage is stable (12.4–14.5 V) during tests
Visually inspect connectors and wiring at the affected door and sill harnesses for damage or corrosion
Check fuses and module power/ground at the door module connector
Use a scan tool / CAN bus analyzer to monitor the bus for the expected frame ID and frequency
Measure CAN_H and CAN_L idle voltages and differential with a meter/oscilloscope (recessive ~2.5 V each, dominant differential ≈ ±2 V)

Expected frame: periodic CAN message from door module (consult vehicle data for exact CAN ID)
Typical frequency: 1–20 Hz depending on signal (door state often 1–10 Hz; streaming sensors vary)
Payload: bits/bytes carrying door open/closed, lock/unlock state, window position, mirror status (format varies by manufacturer)
Electrical: high-speed CAN differential signaling; recessive ~2.5 V on CAN_H and CAN_L, dominant move CAN_H higher and CAN_L lower (differential ≈ 2 V)
Timing: message timeout often flagged when several expected frames are missed (examples: 3–10 consecutive frame misses)
Termination: two 120 Ω resistors (one at each end) giving ~60 Ω across CAN_H and CAN_L

Read and record all DTCs and freeze-frame data from BCM and any door module(s). Note the exact missing message ID if provided.
Verify battery voltage and verify power/ground at the door module connector(s). Replace blown fuses as needed.
Perform visual inspection of door wiring, connectors, body harness grommets, and contact points for corrosion, pin damage or broken wires.
With a scan tool or CAN bus sniffer, monitor CAN traffic and confirm whether the specific door-module CAN ID is present. Note frequency and payload changes.
If message is absent, use an oscilloscope to probe CAN_H and CAN_L near the BCM and at the door module to verify physical signaling and differential levels.
Check bus termination resistance with power off: expect ~60 Ω across CAN_H and CAN_L for high-speed CAN. Repair missing/incorrect terminators.
Unplug the door module (with ignition off) and inspect connector pins for damage; plug back in and re-test. If a known-good spare door module is available, swap to see if message appears.
If bus shows 'bus-off' or excessive errors, isolate segments by disconnecting nodes one at a time while monitoring traffic to find the faulting module or short.
Repair wiring/connector faults and replace failed module(s) as indicated. Reprogram or update module software if configuration mismatch is suspected.
Clear codes and perform a full system retest, including cycling doors and exercising affected features while monitoring for reappearance of the message/DTC.