B0170

Code

Generic B — Body

Body Control Module: Internal Fault

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 19 RU: 12

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Page language: EN

Causes

BCM internal hardware failure (processor, memory, internal circuits)
Corrupted BCM software or failed firmware update
Intermittent or low battery/poor power supply to BCM
Corroded, loose or damaged BCM connectors or wiring (power, ground, CAN/LIN)
Battery disconnects or spikes (jump start events, incorrect battery replacement)
Shorts or opens on input/output circuits causing internal fault detection

Symptoms

Illumination of warning lamp(s) related to body systems (e.g., BCM/INFO light)
Loss or intermittent operation of body functions (door locks, interior lights, wipers, exterior lights)
Multiple modules showing communication errors on a scan tool
Stored related communication or subsystem trouble codes (U-codes or additional B-codes)
Vehicle may crank normally but some convenience features are inoperative

What to check

Connect a quality scan tool and read all stored and pending DTCs and freeze frame data
Record battery voltage with key ON and engine off and during cranking (good battery ≈12.6 V at rest, >9.5 V while cranking)
Inspect BCM connector for corrosion, bent pins, moisture, or water intrusion; check harness for damage or chafing
Verify BCM power and ground circuits: fuses, relays, and continuity to battery and chassis ground
Check CAN and LIN bus activity with a scan tool or oscilloscope; verify presence of expected modules on the network
Check for recent battery replacement, jump start, or attempted module programming that could correlate with failure

Signal parameters

Battery/resting voltage: ~12.4–12.8 V (key off). Key ON/system active: ~12.6–14.4 V (depending on charging)
Cranking voltage should not drop below ~9.5 V (to avoid spurious BCM faults)
CAN bus differential idle voltage: approx. 2.5 V on each CAN high/low with ~2.5 V differential (use scope or graphing tool)
LIN bus idle ~0–12 V single-wire pulses (manufacturer dependent)
Ground resistance should be low (
BCM wake/sleep signals as shown by scan tool: module should respond to wake commands and respond to requests (no constant timeout)

Diagnostic algorithm

Retrieve all codes and freeze-frame data with a capable scan tool; save results. Check for related U-codes or other B-codes.
Verify battery condition and charging system. Charge battery or perform load test if voltage marginal. Re-test for code presence after stable power restored.
Visually inspect BCM connectors and harness for corrosion, water intrusion, damage, or rodent chew. Disconnect battery negative before disconnecting connectors unless manufacturer procedures differ.
Check fuses and power/ground continuity to BCM. Repair any open circuits or high resistance grounds. Reconnect battery and re-scan.
Check vehicle communication buses: verify CAN/LIN activity and that other modules are present and communicative. Repair bus faults (shorts/opens/terminations) before further BCM work.
If wiring and power/communication are good, attempt to clear codes and operate affected functions. If code returns immediately or intermittently, capture occurrence conditions (voltage, vehicle state).
If available, check for and apply BCM software updates or reflash per manufacturer service procedure. Use correct programming equipment and follow anti-theft immobilizer precautions and coding procedures.
If reflash fails or module still reports internal fault after power/communication verified, consider BCM replacement. Follow proper pairing/coding procedures and reprogram to vehicle; restore configurations and code all modules if required.
After repair or replacement, perform full system re-check, clear codes, and verify all body systems and network communications operate normally. Document steps and parts replaced.