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Home / DTC / B2A02 — Body Control Module Fault

B2A02 — Body Control Module Fault

Detailed page for trouble code B2A02.

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B2A02

Generic B — Body

Body Control Module Fault

Brand: Generic
Type: B — Body
Views: UK: 4 EN: 5 RU: 7
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Page language: EN

Causes

  • Low or unstable battery voltage / poor battery connections
  • Blown fuse or failed relay supplying the BCM
  • Corroded, loose, or damaged BCM connector(s) or wiring harness
  • Poor ground connection to the BCM chassis/body ground
  • CAN/LIN bus short or open, high bus error rate
  • Water intrusion or physical damage to the BCM

Symptoms

  • Multiple body electrical functions operating intermittently or not at all (lights, locks, wipers, windows)
  • Warning messages on instrument cluster related to body systems
  • Keyless entry, remote start, or immobilizer faults
  • No communication with BCM via a scan tool or intermittent communication
  • Interior lights, courtesy lights, or dome functions failing
  • Uncommanded outputs or lamps staying on

What to check

  • Read and record all stored DTCs and freeze frame data from all modules on the vehicle network
  • Check battery voltage and state of charge (resting and cranking voltage)
  • Visually inspect BCM connector(s) and harness for corrosion, damage, water, or loose pins
  • Verify fuses and relays feeding BCM power and ignition-switched supply circuits
  • Check chassis and engine ground connections for tightness and corrosion
  • Use a scan tool to monitor CAN/LIN network status and message rates; note any other modules reporting communication faults

Signal parameters

  • Battery supply to BCM: approx. 11.5–14.5 V (engine running/charged)
  • Ignition-switched supply to BCM: battery voltage presence when key ON
  • Ground continuity: body ground to BCM chassis < 0.5 Ω ideally
  • CAN bus differential voltages: idle ≈ 2.5 V on each CAN_H/CAN_L (CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V) and correct dominant/recessive transitions
  • LIN bus idle voltage: near battery voltage when idle; proper frame timing for messages
  • Module wake/sleep state transitions and message frequency (packets/sec) as indicated by factory data

Diagnostic algorithm

  1. Connect a capable scan tool. Retrieve and save all BCM and network-related codes and freeze frame data. Note time stamps and any related U-codes (communication codes).
  2. Check battery voltage (with vehicle off and key on). If voltage is low (
  3. Visually inspect BCM connector(s), wiring, and nearby harness for damage, corrosion, or signs of water intrusion. Inspect fuses/relays feeding the module and replace if blown.
  4. Verify power and ground at the BCM harness pins: measure battery feed and ignition-switched feed, and check ground resistance to chassis. Repair poor connections as needed.
  5. Monitor CAN/LIN communication using a scan tool and/or oscilloscope. Look for missing messages, high error frames, or bus voltages out of expected ranges. Isolate any shorted or loaded nodes if bus faults present.
  6. If communication is intermittent, perform a wiggle test on harness and connectors while monitoring live data to locate wiring faults.
  7. Check for related modules reporting faults (U0100, U0073, U0140, etc.). Disconnect suspected aftermarket devices that may be loading the network and re-evaluate.
  8. If power/ground/communication wiring checks are good and no external cause is found, attempt BCM software verification and reflash/update per manufacturer procedures. Clear codes and test drive to replicate.
  9. If the fault persists after wiring and software steps, consider replacement of the BCM. Follow dealer/manufacturer procedures for replacing and programming the BCM to the vehicle, then recheck all functions.
  10. After repair, erase codes, perform network relearn or module initialization procedures (as required), and confirm repair by verifying no reoccurrence and proper operation of body systems.

Likely causes

  • Poor battery or charging system voltage causing BCM reboot or faults
  • Loose or corroded BCM connector pins or damaged wiring at a harness splice
  • Ground strap or ground point with high resistance
  • High error count or lost messages on the CAN/LIN network to which the BCM is connected
  • BCM firmware corruption requiring reflash or calibration
  • Moisture intrusion causing intermittent shorts inside the BCM enclosure

Fault status

⚠️ Status
BCM reported an internal fault or communication/power/ground anomaly. Code stored when the module detected abnormal internal status, supply/ground loss, or unreliable network communication.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-4.0 hours

Similar codes

B2A00 B2A01 B2A03 U0100 U0073 U0140
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