B105C

Code

Generic B — Body

Body Control Module — Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 15 EN: 15 RU: 15

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

BCM internal hardware failure (processor, memory, or internal power regulator)
Corrupted or failed BCM software/firmware or calibration data
Intermittent or low vehicle battery voltage or recent battery disconnect
Power supply or ground circuit faults to the BCM
Water intrusion, corrosion, or physical damage to BCM or connector
Shorts or open circuits in wiring harness to BCM

Symptoms

Multiple body functions intermittent or inoperative (lights, locks, wipers, windows, etc.)
Instrument cluster or other modules show communication errors or warnings
Interior lights, door locks, or remote functions do not respond or behave erratically
Vehicle may not go to sleep or may show excessive battery drain
DTC persists after clearing or returns immediately after power cycle
Possible no-start if BCM handles immobilizer or start authorization

What to check

Read and record all stored codes and freeze-frame data from the BCM and other networks
Check battery state of charge and battery terminal connections; confirm vehicle voltage (12.5–14.5 V with engine running)
Inspect BCM connector(s) for corrosion, bent pins, water intrusion, or damage
Verify BCM power and ground circuits (pin-by-pin) for proper voltage and low resistance to chassis
Scan CAN/LIN bus for communication errors, lost messages, or bus voltage abnormalities
Review vehicle history for recent battery disconnects, jump starts, or aftermarket installs

Signal parameters

Battery/supply voltage at BCM (Key OFF/ON/Run ranges)
Ground resistance between BCM ground terminal and chassis (should be low)
CAN bus voltage and activity (dominant/recessive levels, message counts)
LIN bus signals (if applicable) and message presence
Wake/sleep request signals and module wake counts
Internal module status flags: checksum/EEPROM error, software version, reset count (if available)

Diagnostic algorithm

Verify code: Use a capable scan tool to read B105C and related codes from all modules. Record freeze frame and occurrences.
Battery/Power check: Confirm battery health and voltage. Recharge or replace weak battery before continuing.
Visual inspection: Remove BCM access cover and inspect connectors and PCB area for corrosion, water, or physical damage.
Power/ground verification: With ignition OFF and key ON, measure supply voltage and ground at BCM connector pins. Repair any open/poor grounds or high resistance feeds.
Communications check: Monitor CAN/LIN traffic; note missing frames, errors, or bus off conditions. Repair wiring or short circuits on BUS if found.
Clear codes and reproduce: Clear codes, cycle ignition, and exercise body functions to try to reproduce the fault. Note whether B105C returns and under what conditions.
Software check: Verify BCM software/calibration level. If a manufacturer update or reflash is available for internal error or checksum issues, follow OEM reprogramming procedures.
Isolate external causes: Disconnect non-OEM accessories and check for improvement. Verify immobilizer or hybrid system interactions if applicable.
Module reset/reprogram: If allowed by OEM, perform a controlled reset or reflash. If reprogramming fails or error persists, replacement of BCM may be required.
Replacement and coding: If replacement is necessary, install a programmed/re-coded BCM per manufacturer procedures and perform required adaption/relearn procedures for keys, modules, and settings.
Verification: After repair or replacement, clear codes, confirm normal operation of body systems, and road test to ensure fault does not return.

Likely causes

Internal BCM memory corruption or failed EEPROM
Loose/bad ground or power feed to the BCM causing resets or errors
CAN bus communication errors preventing normal operation
Water damage or connector corrosion at the BCM
Faulty BCM hardware requiring reflash or replacement

Fault status

⚠️ Status

Internal fault detected in Body Control Module (BCM). Module reported internal error or memory corruption. Verify power, grounds, communications, and module integrity; reprogram or replace BCM if issue persists.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5 - 4.0 hours