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Home / DTC / B0170 — Body Control Module: Internal Fault

B0170 — Body Control Module: Internal Fault

Detailed page for trouble code B0170.

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B0170

Generic B — Body

Body Control Module: Internal Fault

Brand: Generic
Type: B — Body
Views: UK: 3 EN: 8 RU: 6
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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

  1. Retrieve all codes and freeze-frame data with a capable scan tool; save results. Check for related U-codes or other B-codes.
  2. Verify battery condition and charging system. Charge battery or perform load test if voltage marginal. Re-test for code presence after stable power restored.
  3. Visually inspect BCM connectors and harness for corrosion, water intrusion, damage, or rodent chew. Disconnect battery negative before disconnecting connectors unless manufacturer procedures differ.
  4. Check fuses and power/ground continuity to BCM. Repair any open circuits or high resistance grounds. Reconnect battery and re-scan.
  5. 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.
  6. 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).
  7. 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.
  8. 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.
  9. 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.

Likely causes

  • Poor battery voltage or unstable power supply to BCM (including blown fuses)
  • Corroded or loose BCM connector pins or wiring harness damage
  • CAN or LIN bus communication fault (lost or noisy bus)
  • Software corruption or failed module update
  • Internal BCM hardware failure requiring replacement

Fault status

⚠️ Status
BCM reports an internal fault; module detected an internal hardware or software malfunction or an unreliable power/communication environment.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-5 hours

Similar codes

B0100 B0171 U0100 U0140 B0120
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