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Home / DTC / B16A3 — Body Control Module — Internal Fault (B16A3)

B16A3 — Body Control Module — Internal Fault (B16A3)

Detailed page for trouble code B16A3.

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Code

B16A3

MITSUBISHI B — Body

Body Control Module — Internal Fault (B16A3)

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
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Completed 100%
Page language: EN

Causes

  • BCM internal hardware failure (logic, memory, or processor fault)
  • Corrupted or failed BCM software/firmware
  • Low or unstable supply voltage to the BCM (battery, charging system)
  • Poor ground or intermittent power supply to the BCM
  • Water intrusion, corrosion, or physical damage to BCM or connectors
  • Damaged wiring, short to battery or ground, or high resistance in power/ground circuits

Symptoms

  • Multiple body functions unreliable or inoperative (lighting, wipers, door locks, windows)
  • Related warning lights or messages on instrument cluster
  • Loss of communication with BCM on diagnostic scanner (U-codes may also appear)
  • Intermittent electrical symptoms (random relays, locks, lamps switching)
  • Possible no-start or immobilizer related faults if BCM interfaces with security

What to check

  • Read and record all stored DTCs and freeze frame data with a capable scan tool
  • Check battery voltage with key on/engine off and during cranking (should be ~12.4–12.8 V idle, >9.5 V during cranking)
  • Inspect BCM connectors and harness for corrosion, water entry, bent pins, or loose connectors
  • Verify fuses and power relays supplying the BCM are good and have proper continuity
  • Check main ground(s) for the BCM for tightness and low resistance to chassis/negative battery
  • Check CAN/LIN communication lines for bus errors, termination, and correct voltages

Signal parameters

  • BCM supply voltage (expected ≈ 12 V with key ON; stable within vehicle tolerances)
  • BCM ground continuity (near 0 ohms to chassis/negative battery)
  • CAN High/CAN Low common-mode voltage (~2.5 V) and differential signaling present when network active
  • CAN bus data frames: modules present, error counters, bus-off status
  • LIN or other serial bus activity if BCM interfaces with subnets (presence/idle levels)

Diagnostic algorithm

  1. Connect a manufacturer-capable scan tool and read all DTCs from BCM and other modules; save codes and freeze-frame data.
  2. Verify whether the code is current/active or stored/historic. If historic, note conditions and try to reproduce.
  3. Check battery voltage and charging system; ensure battery is charged and terminals clean and tight.
  4. Inspect BCM connector and wiring for corrosion, bent pins, water ingress, or damaged insulation. Repair any damage found.
  5. Verify fuses and power/ground circuits to the BCM: measure voltage at BCM power pins and continuity to ground.
  6. Check communication lines (CAN/LIN): observe bus with scan tool or oscilloscope for frames, error flags, and correct voltages; look for bus-off conditions or high error counts.
  7. If power/ground and bus are good, attempt to clear code and monitor if B16A3 returns during normal operation or specific function tests.
  8. Check for available BCM software/firmware updates or TSBs; reflash or reprogram BCM per manufacturer procedure if recommended.
  9. If reprogramming fails or module continues to report internal fault after confirming external systems are good, consider replacing the BCM and performing required programming/configuration. Follow OEM procedures for replacement and immobilizer/security pairing.
  10. After repair or replacement, re-scan all modules and perform a full systems check to ensure no residual faults remain.

Likely causes

  • Corrupted firmware or software fault inside BCM
  • Poor power/ground to the BCM (low battery voltage, blown fuse, bad ground)
  • Corrosion or water damage to BCM or connector pins
  • Intermittent wiring fault causing voltage spikes or dropouts

Fault status

⚠️ Status
Body Control Module internal fault detected — module self-diagnostic reports an internal error or invalid internal state.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5-4.0 hours

Similar codes

B16A0 B16A1 B16A2 U0100 U0073 U0121
406

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