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Home / DTC / B2645 — B2645 — Manufacturer-specific body control code (refer to service manual)

B2645 — B2645 — Manufacturer-specific body control code (refer to service manual)

Detailed page for trouble code B2645.

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Code

B2645

HUMMER B — Body

B2645 — Manufacturer-specific body control code (refer to service manual)

Brand: HUMMER
Type: B — Body
Views: UK: 18 EN: 29 RU: 18
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Page language: EN

Causes

  • Faulty or intermittent Body Control Module (BCM) hardware
  • Corroded, loose or damaged BCM connector or wiring harness
  • Low or intermittent battery/charging system voltage
  • CAN/LIN bus communication fault or bus termination issue
  • Water intrusion or physical damage to BCM or connectors
  • Aftermarket accessories or poor repairs affecting BCM circuits

Symptoms

  • One or more body functions operate intermittently or fail (door locks, interior lights, wipers, etc.)
  • Multiple body-related warning messages or indicators present
  • Parasitic battery drain or unexpected battery discharge
  • No communication with BCM when scanning the vehicle
  • Random or recurring manufacturer-specific B-codes stored

What to check

  • Use a factory-level or high-quality scan tool to read B2645 plus any additional stored U/B codes and freeze-frame/extended data
  • Record BCM status, VIN and module presence on CAN/LIN using the scan tool
  • Visually inspect BCM and related connector(s) for corrosion, bent pins, water entry or physical damage
  • Check battery voltage and charging system under key-on and cranking conditions (nominal ~12.6V at rest, ~13.5–14.8V charging)
  • Check for aftermarket installations or recent body repairs that may have disturbed wiring
  • Perform wiggle/wear tests on harness with technician observing live data for intermittent faults

Signal parameters

  • BCM primary power: battery voltage (nominal ~12–14.8 V under typical conditions)
  • BCM ground continuity: near 0 ohms to chassis ground
  • CAN bus idle voltages: approximately 2.5 V on CANH and CANL differential ~0 V (verify proper differential and message activity)
  • LIN bus idle voltage: ~12 V or manufacturer-specific pull-up (check service manual)
  • Module presence: BCM should respond to scan tool and show expected diagnostic data and IDs
  • Current draw: parasitic draw when vehicle is asleep (compare to spec in service manual)

Diagnostic algorithm

  1. Connect an appropriate scan tool and retrieve B2645, all related codes, freeze-frame and live data. Note when the code was set and any accompanying codes.
  2. Verify battery state-of-charge and charging system operation. Recharge or replace battery if voltage is low, then retest.
  3. Inspect BCM connector and mating harness for corrosion, moisture, bent pins or damaged seals. Repair or reseal as required.
  4. Backprobe power and ground pins at the BCM to verify stable supply voltage and good ground during key-on, cranking and while exercising affected functions. Repair wiring if intermittent or out of spec.
  5. Monitor CAN/LIN bus traffic while exercising affected systems. Look for missing messages, error counters, bus short to battery/ground or incorrect termination. Repair bus faults.
  6. Remove or disable any aftermarket accessories that could interfere with BCM circuits and retest.
  7. Clear codes and attempt to reproduce the fault. If code returns, record conditions and times. Try to capture intermittent behavior with data logging or scope.
  8. If wiring, power/ground and communication checks pass and the code persists, consult the manufacturer service manual for the specific B2645 diagnostic routine (may include BCM reprogramming or configuration).
  9. As a last resort, and only after following factory diagnostic procedures, consider module replacement; ensure software calibration/programming match vehicle VIN and options.
  10. After repair or replacement, verify normal operation, clear codes, and perform recommended post-repair checks (long-term monitoring if intermittent).

Likely causes

  • Intermittent power or ground to the BCM
  • Damaged or corroded BCM connector pins
  • CAN-bus communication error between BCM and other modules
  • BCM internal fault or firmware corruption

Fault status

⚠️ Status
Manufacturer-specific body control diagnostic trouble code stored in the BCM. The code indicates a condition defined by the manufacturer; refer to the HUMMER service manual for the precise code definition and step-by-step tests. May be stored as active, pending or history depending on event conditions.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

B2640 B2641 B2646 B2630 U0100 U0121
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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