B2901

Code

Generic B — Body

Body Control Module — Internal Error

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 22 RU: 11

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

BCM internal hardware failure (processor, memory, I/O circuits)
Corrupted or failed BCM firmware/software
Intermittent or low battery/voltage supply to BCM
Poor chassis or battery ground at BCM
Water intrusion or corrosion in BCM connector or housing
Physical damage to module or PCB

Symptoms

Multiple body systems inoperative or intermittent (locks, lights, windows, wipers, HVAC controls)
Warning indicators on dash or multiple module fault messages
Loss of communication with BCM on diagnostic scanner (U0140/U0100 related symptoms)
Unknown or incorrect behavior from convenience systems (keyless entry, interior lights)
Vehicle may fail to enter sleep/wake states or show excessive battery drain

What to check

Retrieve all stored DTCs and freeze-frame data from BCM and other modules with a scanner
Check battery voltage with key on and engine off and during cranking; note any drops or fluctuations
Inspect BCM connector(s) for corrosion, bent pins, water intrusion, or damage
Verify all BCM fuses and related power feeds are intact and correct amperage
Check main ground(s) and measure resistance between BCM ground and chassis/negative battery (should be low)
Scan CAN/LIN networks for communication errors and active error counters

Signal parameters

Battery/supply voltage at BCM: nominal ~12–14.8 V (engine running and key on)
Cranking voltage: not excessively low; avoid large dips below ~9–10 V
Ground resistance: low (typically
CAN bus activity: modules should be communicating; look for valid CANH/CANL voltages and differential signal
LIN or serial communication levels if used by BCM (refer to vehicle spec)
PCM/other-module communication status: count of lost frames or timeouts reported by scan tool

Diagnostic algorithm

Confirm B2901 with a full module scan and note any additional codes (do not clear yet)
Record freeze-frame and current parameter data for reference
Verify battery state of charge and charging system; recharge or replace battery if needed to ensure stable voltage
Visually inspect BCM and connectors for moisture, corrosion, heat damage, or loose retainers; repair or replace damaged connectors/wiring
Check and clean ground connections; tighten mounting hardware and re-check resistance to chassis
Check fuses and fusible links feeding the BCM; restore any blown circuits and then retest
Use a scan tool to monitor BCM communication; if bus is silent, trace CAN/LIN power, termination resistors, and wiring back to other modules
If wiring, power and grounds are good, attempt a controlled module reset (battery disconnect per service manual) or power-cycle via scan tool if supported
Check for available technical service bulletins (TSBs) or software updates; if a recent reflash failed, attempt proper reprogramming using OEM procedure
If module still reports internal error after correct power/ground/communication, consider replacement or bench repair; have replacement BCM programmed/configured to vehicle specifics before final installation
After repair or replacement, clear codes and perform full function test and road test to confirm resolution

Likely causes

Battery or charging system low/unstable voltage
Loose, corroded or damaged BCM power/ground connectors
Failed BCM memory or processor due to age or thermal stress
Recent failed or interrupted software update/reflash
Water intrusion or evident corrosion at BCM connector

Fault status

⚠️ Status

BCM internal fault detected — may affect multiple body systems and communications; requires inspection of power, grounds, wiring, and possible reflash or replacement of module.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.0 - 4.0 hours