B0220

Code

Generic B — Body

Body Control Module Subsystem Fault

Brand: Generic

Type: B — Body

Views: UK: 14 EN: 17 RU: 11

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Internal BCM hardware or software failure
Low or intermittent battery voltage / poor charging system
Blown fuse or faulty power feed to the BCM
Corroded, loose or damaged BCM connector or wiring harness
Poor engine/chassis ground at BCM or related ground points
CAN/LIN bus communication fault (open, short, missing termination)

Symptoms

Multiple body functions inoperative or intermittent (lighting, locks, windows, wipers, HVAC blower control)
Malfunction indicator lamps or message center warnings related to body systems
Loss of communication with BCM on diagnostic scanner
Erratic behaviour of vehicle convenience features
Possible no-crank/no-start if BCM is integral to starter/immobilizer

What to check

Read all stored and pending codes from all modules; capture freeze frame and history
Verify battery state of charge and charging system voltage (engine running ~13.5–14.5 V)
Inspect BCM fuses and relays; check for blown fuses and correct fuse values
Visually inspect BCM connector and wiring for corrosion, bent pins, damage, or water ingress
Check main grounds near BCM and chassis grounds for continuity and corrosion
Use a scan tool to check if BCM is present on the network and monitor CAN/LIN traffic

Signal parameters

Supply voltage to BCM: nominal 12 V (acceptable ~11–14.5 V under load)
Ground resistance at BCM ground: < 0.1 Ω preferred
Key-on battery drain/current draw for BCM in sleep: manufacturer specific (watch for excessive parasitic draw)
CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); differential resistance ≈ 60 Ω across CAN_H/CAN_L
LIN bus idle voltage and wake patterns as per vehicle spec (if applicable)
Module presence on network: module should respond to diagnostic requests and publish expected PIDs

Diagnostic algorithm

Connect a scan tool and read all codes from BCM and other modules; note any U-codes or related B-codes.
Verify battery voltage and charging system health; ensure battery ≥ 12 V for diagnostics.
Inspect BCM fuses/relays and replace any blown items; recheck after replacement.
Visually inspect BCM connector and harness for water, corrosion, damaged insulation or repairs; repair any issues.
Check and repair chassis and engine grounds near BCM; clean and tighten ground connections.
With key ON, use a multimeter/oscilloscope to measure CAN_H and CAN_L voltages and check for proper termination (~60 Ω). Look for bus errors on the scan tool.
If communications are lost, isolate by disconnecting suspected nodes or aftermarket devices and observe if communication is restored.
If wiring and power/ground are good, attempt to communicate with BCM using manufacturer-level diagnostic tool; check for available software updates or reflash history.
If BCM does not respond or shows internal errors after wiring and power verified, follow manufacturer procedure for module programming/replacement. Replace and program BCM only after confirming root cause.
Clear codes and test drive; verify restoration of functions and monitor for recurrence.

Likely causes

Loss of stable supply voltage or poor ground at BCM
Faulty or intermittent CAN bus (short, open, missing termination)
Corroded/loose BCM connector pins or damaged wiring
Software/firmware corruption in BCM needing reflash
Internal BCM component failure (requires replacement)

Fault status

⚠️ Status

BCM subsystem fault — internal error or communications/power fault detected. Investigate power, grounds, wiring, and network communications before module replacement.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5–4.0 hours

Repair manuals