B231A

Code

Generic B — Body

Body Control Module Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 17 EN: 22 RU: 12

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Internal processor or memory failure inside the BCM
Corrupted or failed firmware/software
Intermittent or out-of-range supply voltage to the BCM
Damaged or corroded power/ground/communication connectors
Water intrusion or physical damage to the BCM
Electrostatic or thermal damage from past events

Symptoms

One or more body functions inoperative (lighting, door locks, windows, wipers, interior lights, etc.)
Malfunction indicator or BCM-related warning lamp illuminated
Loss or intermittent loss of communication with BCM on scan tool (no response)
Unexpected module resets or repeated fault codes
Parasitic battery drain when vehicle is off
Erratic or intermittent operation of systems controlled by BCM

What to check

Verify battery state of charge and resting voltage (12.4–12.8 V typical) and cranking voltage (can drop to 9–11 V while cranking)
Inspect BCM power and ground pins for corrosion, loose terminals, or water damage
Check associated fuses and fusible links for the BCM power feeds
Scan vehicle with a capable diagnostic tool and record all DTCs and freeze frame data from BCM and other modules
Verify CAN/LIN bus communication: check for normal idle voltages and message traffic; look for bus errors or collisions
Measure supply voltage at the BCM power pin with key on and engine running; check for excessive voltage drop

Signal parameters

Main supply voltage to BCM (key on): typically ~11.5–14.5 V; significant deviation can cause faults
Cranking voltage: may drop to ~9–11 V; sustained low voltage can corrupt module memory
Sleep or quiescent current draw: BCM should draw very low current when asleep (varies by vehicle, commonly
CAN bus idle voltages: CANH ≈ 2.5 V, CANL ≈ 2.5 V; dominant state ~CANH 3.5 V / CANL 1.5 V — check for proper differential signaling
Ground resistance: low resistance to chassis ground (
Communication response time: BCM should respond promptly to diagnostic requests; long delays or no response indicate internal or bus issues

Diagnostic algorithm

Record all stored DTCs and freeze-frame data from the BCM and other modules; note any related U-codes (communication faults).
Verify battery condition and proper system voltage. Charge or replace battery if voltage is low; ensure terminals are clean and tight.
Inspect BCM connector(s) and wiring for damage, corrosion, loose pins, or water intrusion; repair any damage and re-test.
Check fuses and power feeds to the BCM; measure voltage at the module power pin with ignition on and engine running.
Verify ground integrity at BCM ground pins (measure resistance to chassis ground); repair poor grounds.
Use a diagnostic tool to check network traffic on CAN/LIN and attempt to communicate with the BCM; note any bus errors or absence of messages.
If communications are present but the BCM reports internal errors, attempt a soft reflash or software reprogram per OEM procedure (only with manufacturer-approved tool and files).
If a reflash fails or the BCM does not respond to programming, perform module bench or in-vehicle replacement following OEM coding and pairing procedures.
After any repair or replacement, clear codes, perform relearn/coding steps required by the manufacturer, and retest all body functions and network communication.
If intermittent failures persist, perform wiggle tests on harnesses while monitoring communication and power, and consider environmental stress (heat/cold/water) testing.

Likely causes

Low battery or poor battery connections causing brownout
Blown fuse or high-resistance ground feeding the BCM
CAN/LIN network short or severe bus errors triggering internal fault
Failed firmware update or interrupted programming event
Corrosion or water ingress at BCM connector(s)
Electrical surge (jump start, improper charging) damaging internal components

Fault status

⚠️ Status

BCM internal fault detected — module self-test failure (processor/memory/firmware). BCM may be unresponsive or intermittently functional; inspect power, ground, connectors, and software.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4.0 hours