B3790

Code

Generic B — Body

Body Control Module Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 17 EN: 19 RU: 11

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty BCM hardware (internal component failure)
Corrupted BCM firmware or software
Low or unstable battery voltage/power surge
Poor power or ground connections to BCM
Water ingress or corrosion at BCM connectors or housing
CAN/LIN bus electrical faults or excessive error frames

Symptoms

Malfunction indicator lamp (MIL) or warning lamp related to body systems
Multiple body functions inoperative or intermittent (door locks, lights, wipers, windows)
Unable to communicate with BCM over diagnostic tool (timeout or intermittent)
Fuses related to BCM blowing or unusual parasitic battery drain
Stored additional DTCs for related systems (locks, lighting, instrument cluster)

What to check

Read DTCs and freeze frame data with a capable scan tool; save module reports
Check for other related module codes and communication errors (time-outs)
Verify battery voltage at rest and with engine cranking (12.4–12.9 V nominal)
Inspect BCM connector and harness for corrosion, bent pins, damaged wires, water intrusion
Check BCM fuses and relays for continuity and correct amperage
Measure supply voltage and ground at BCM connector with key on/off; wiggle harness to reproduce fault

Signal parameters

Supply voltage to BCM (key OFF/ON/RUN)
Supply ground resistance and continuity
BCM supply current / parasitic draw (mA)
CAN bus voltage levels and error frame count
LIN bus activity (if equipped)
Number and type of internal resets/watchdog events in BCM history

Diagnostic algorithm

Connect a scan tool and record B3790 details, freeze frame, and any related codes. Check for software updates or TSBs for BCM. 2) Verify battery state of charge and charging system. Recharge or replace battery if low and retest. 3) Visually inspect BCM module and connector for water, corrosion, damaged pins, or heat damage. Repair harness as needed. 4) Verify power and ground: measure key OFF/ON supply voltage at BCM pins and ground resistance to chassis. Repair poor connections. 5) Scan bus traffic: monitor CAN/LIN for noise, error frames or bus short — isolate by disconnecting modules as required. 6) Perform wiggle and continuity tests on harness while monitoring scan tool for code changes. 7) If intermittent persists after power/ground and bus checks, attempt BCM software/firmware reflash or reprogram per OEM procedures. 8) If reprogramming fails or diagnostics show internal hardware faults (persistent CRC, memory errors, repeated watchdog resets), replace BCM with a known-good unit and program/configure according to factory procedure. 9) After repair, clear codes, verify operation of all body systems, and road-test to confirm no reoccurrence before closing job.

Likely causes

Failed internal processor, memory (EEPROM/Flash) corruption or CRC error
Intermittent/low supply voltage (weak battery, loose connector) causing resets
Short to ground or short to battery on BCM power feed
Corroded or damaged BCM connector pins causing intermittent contacts
CAN bus short or heavy noise causing internal watchdog trips

Fault status

⚠️ Status

B3790 indicates an internal fault detected by the Body Control Module — a hardware or software malfunction inside the BCM. It may cause loss or degradation of body functions and communications with other modules.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4.0 hours