B0138

Code

Generic B — Body

Body Control Module — Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 4 EN: 10 RU: 3

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Internal BCM hardware or firmware failure
Corrupted module software or configuration
Low or intermittent battery voltage / voltage spike
Poor power or ground connections to the BCM
Damaged wiring harness or connector corrosion
Water intrusion or physical damage to the BCM

Symptoms

Multiple body functions not working (lights, wipers, door locks, windows, etc.)
Intermittent or permanent loss of BCM communication on scan tool
Fuses blowing or relays not operating despite correct inputs
Warning lamps illuminated (e.g., body control warning, multiple module communication warnings)
Vehicle may not go to accessory or start modes correctly

What to check

Read the full freeze frame and current codes with a diagnostic scan tool that supports the BCM
Verify battery state of charge and charging system (battery voltage at rest and cranking)
Verify constant and switched power at BCM supply pins (VBATT and IGN) with key on/off
Check BCM ground(s) for continuity to chassis (
Inspect BCM connectors and wiring for corrosion, bent pins, water damage, or rodent damage
Check related fuses and relays; test for proper input and output voltages

Signal parameters

VBATT (module supply voltage) — expected ~12.0–14.5 V when running
IGN/switched supply presence when key on
Ground continuity / voltage drop on ground circuit
CAN bus differential voltage — idle ~2.5 V on each CAN line, proper bus activity
BCM 'Alive' / response frequency on network (should appear on scan tool)
Internal module temperature or error counters if available via OEM scanner

Diagnostic algorithm

Connect a capable scan tool and retrieve all codes, freeze frame data, and BCM events. Record software/part numbers.
Clear codes and attempt to re-run tests to check for persistence or intermittent behavior.
Measure battery voltage (resting and with starter). If low, charge or replace battery before further diagnosis.
With ignition on, measure VBATT and IGN supplies at the BCM connector; confirm voltages match battery and key position.
Measure ground resistance from BCM ground pins to chassis; repair any high-resistance grounds.
Visually inspect and back-probe connectors for corrosion, bent pins, or moisture. Repair or replace damaged connectors/harness sections.
Check all related fuses and relays for continuity and correct operation. Replace any faulty items.
Check CAN/LIN network health: verify termination resistances, confirm presence of other modules and BCM 'alive' messages. Repair bus faults.
If power, ground, wiring and network are good, check for available software updates and attempt a module reflash/reprogram with OEM tool per service procedure.
If reflash fails or code persists after good power/ground/network and confirmed latest software, consider replacing the BCM and perform required coding/programming and key/feature relearn per manufacturer instructions.

Likely causes

Corrupted firmware or software bug requiring reflash
Intermittent VBATT or ground at BCM causing internal errors
Damaged / corroded connector pins or harness at BCM
Previous repair or jump-start event that caused voltage transient
Actual internal hardware fault in the BCM module

Fault status

⚠️ Status

BCM internal fault detected — module self-test or diagnostics reported an internal error. Check power, grounds, connectors, communication bus, and software before replacing the module.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.0-3.0 hours