Code
B2551
Generic
B — Body
Body Control Module Internal Fault
AI status
Completed
Completed
100%
Causes
- BCM internal hardware failure (component or PCB damage)
- Corrupted or failed BCM software/firmware
- Intermittent or low battery voltage / poor power supply
- Poor ground or corroded connector pins
- Water intrusion or physical damage to BCM
- Shorts, opens, or wiring harness damage to BCM power/ground or data lines
Symptoms
- Multiple body electrical functions intermittent or inoperative (lights, locks, windows, wipers)
- BCM does not respond to diagnostic scan tool or reports internal error
- Random fault codes or recurring body/control module errors
- Instrument cluster warning lights related to body/control systems
- Vehicle security/immobilizer faults or unexpected behavior
- Battery drain or abnormal electrical behavior
What to check
- Read and record all stored and pending DTCs and freeze frame data with a capable scan tool
- Check battery state of charge and system voltage (engine off and running)
- Inspect BCM connectors for corrosion, bent pins, water intrusion, and secure fit
- Verify main fuses and relay(s) for BCM power circuits
- Check ground points and continuity from BCM ground to chassis/engine ground
- Scan for communication errors (lost messages, bus off) on CAN/LIN networks
Signal parameters
- Battery supply to BCM: ~12.0 V (engine off); charging system 13.5–14.8 V (engine running)
- Ignition-switched supply present when key/IGN is on (check for expected wake-up voltage)
- Ground continuity: near 0 Ω to chassis ground
- CAN bus idle voltages: approximately 2.5 V on CAN_H and CAN_L (verify differential signaling and traffic)
- CAN/LIN data traffic present when module is awake (use bus monitor to confirm messages)
- No excessive voltage spikes or noise on supply lines under normal conditions
Diagnostic algorithm
- Record all codes and freeze-frame data. Note any additional U- or B-codes that indicate communication issues.
- Verify stable battery voltage and good charging system. Recharge or replace battery if low and retest.
- Visually inspect BCM connector, wiring harness, and grounds. Repair any corrosion, damaged wires, or loose pins.
- Check fuses/relays supplying the BCM and verify ignition-switched power and constant power pins with a DVOM.
- Use a scan tool to verify BCM communication on the vehicle network. Note bus errors, lost messages, or bus-off conditions.
- Clear codes and perform an ignition cycle or drive cycle to see if B2551 returns and under what conditions.
- If communication is intermittent, attempt to isolate by removing aftermarket devices and disconnecting suspect circuits.
- If available, check for OEM software updates or reflash the BCM per manufacturer procedure. Reflash only with correct operating conditions and tool.
- If fault persists after power/ground, wiring and software checks, consider bench testing or replacing BCM with known-good unit and program/configure as required.
- After repair or replacement, verify all body functions, re-scan for codes, and confirm no return of the fault during normal operation.
Likely causes
- Loose or corroded power/ground connector at BCM
- Voltage irregularity (weak battery, bad alternator, poor charging)
- BCM exposed to moisture leading to internal corrosion
- Failed internal memory or processor within BCM
- Recent software update failed or incomplete reflash
Fault status
Status
Internal fault detected in Body Control Module. Module may be malfunctioning, not responding to network communication, or experiencing internal memory/software errors. Further inspection of module power, grounds, connectors, and software is required.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
Similar codes
Repair manuals
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Code
B2551
HYUNDAI
B — Body
Right Head Lamp(Low Beam) Short to Ground
AI status
Completed
Completed
100%
Causes
- BCM internal hardware failure (component or PCB damage)
- Corrupted or failed BCM software/firmware
- Intermittent or low battery voltage / poor power supply
- Poor ground or corroded connector pins
- Water intrusion or physical damage to BCM
- Shorts, opens, or wiring harness damage to BCM power/ground or data lines
Symptoms
- Multiple body electrical functions intermittent or inoperative (lights, locks, windows, wipers)
- BCM does not respond to diagnostic scan tool or reports internal error
- Random fault codes or recurring body/control module errors
- Instrument cluster warning lights related to body/control systems
- Vehicle security/immobilizer faults or unexpected behavior
- Battery drain or abnormal electrical behavior
What to check
- Read and record all stored and pending DTCs and freeze frame data with a capable scan tool
- Check battery state of charge and system voltage (engine off and running)
- Inspect BCM connectors for corrosion, bent pins, water intrusion, and secure fit
- Verify main fuses and relay(s) for BCM power circuits
- Check ground points and continuity from BCM ground to chassis/engine ground
- Scan for communication errors (lost messages, bus off) on CAN/LIN networks
Signal parameters
- Battery supply to BCM: ~12.0 V (engine off); charging system 13.5–14.8 V (engine running)
- Ignition-switched supply present when key/IGN is on (check for expected wake-up voltage)
- Ground continuity: near 0 Ω to chassis ground
- CAN bus idle voltages: approximately 2.5 V on CAN_H and CAN_L (verify differential signaling and traffic)
- CAN/LIN data traffic present when module is awake (use bus monitor to confirm messages)
- No excessive voltage spikes or noise on supply lines under normal conditions
Diagnostic algorithm
- Record all codes and freeze-frame data. Note any additional U- or B-codes that indicate communication issues.
- Verify stable battery voltage and good charging system. Recharge or replace battery if low and retest.
- Visually inspect BCM connector, wiring harness, and grounds. Repair any corrosion, damaged wires, or loose pins.
- Check fuses/relays supplying the BCM and verify ignition-switched power and constant power pins with a DVOM.
- Use a scan tool to verify BCM communication on the vehicle network. Note bus errors, lost messages, or bus-off conditions.
- Clear codes and perform an ignition cycle or drive cycle to see if B2551 returns and under what conditions.
- If communication is intermittent, attempt to isolate by removing aftermarket devices and disconnecting suspect circuits.
- If available, check for OEM software updates or reflash the BCM per manufacturer procedure. Reflash only with correct operating conditions and tool.
- If fault persists after power/ground, wiring and software checks, consider bench testing or replacing BCM with known-good unit and program/configure as required.
- After repair or replacement, verify all body functions, re-scan for codes, and confirm no return of the fault during normal operation.
Likely causes
- Loose or corroded power/ground connector at BCM
- Voltage irregularity (weak battery, bad alternator, poor charging)
- BCM exposed to moisture leading to internal corrosion
- Failed internal memory or processor within BCM
- Recent software update failed or incomplete reflash
Fault status
Status
Internal fault detected in Body Control Module. Module may be malfunctioning, not responding to network communication, or experiencing internal memory/software errors. Further inspection of module power, grounds, connectors, and software is required.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
Similar codes
Repair manuals
Manual library for HYUNDAI
371
Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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