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Home / DTC / B278A — Control Module Internal Fault

B278A — Control Module Internal Fault

Detailed page for trouble code B278A.

34,405codes
59brands
11,914generic
22,491specific
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Code

B278A

Generic B — Body

Control Module Internal Fault

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

Causes

  • Corrupted or failed module software/firmware
  • Internal processor or memory (flash/EEPROM) failure
  • Failed internal power regulator or voltage rail
  • Faulty CAN/LIN transceiver inside the module
  • Intermittent or low supply voltage (battery, fuses, wiring)
  • Water, corrosion, or physical damage to module or connector

Symptoms

  • Malfunction or loss of the functions controlled by the module
  • No communication with the module via scan tool or sporadic responses
  • Illuminated warning lamp(s) or dash messages related to the module
  • Stored B278A and possibly related communication or memory DTCs
  • Intermittent operation or erratic behavior of affected systems

What to check

  • Use a capable scan tool to read B278A plus all stored/freeze‑frame data and related codes
  • Check battery state of charge and battery connections; ensure nominal system voltage (≈12–14 V)
  • Visually inspect module connector, pins and harness for corrosion, bent pins, water intrusion or damage
  • Check relevant fuses, fusible links and power‑distribution relays for continuity
  • Verify module supply and ground voltages at the connector with engine off and cranking
  • Confirm presence and frequency of network messages (CAN/LIN) using scanner or oscilloscope

Signal parameters

  • VBATT at module power pin: ~11–14.5 V (engine off/running as applicable)
  • Ground resistance:
  • Internal 5 V (or module reference rail) if accessible: within manufacturer tolerance
  • CAN bus: expected message IDs for this module present at normal bitrate and periodicity
  • CAN transceiver voltage levels: recessive ~2.5 V, dominant pull low when active
  • Watchdog/reset count: 0 or no frequent unexpected resets (increasing reset count indicates fault)

Diagnostic algorithm

  1. Record DTCs and freeze‑frame data with a professional scan tool. Note any related communication or power DTCs.
  2. Clear codes, then perform a self‑test or key cycles to see if B278A returns immediately or after a specific event.
  3. Verify battery condition and terminal tightness. Repeat with steady nominal battery voltage to rule out low‑voltage corruption.
  4. Inspect connector and harness for contamination, corrosion, bent pins or mechanical damage. Repair or clean as needed.
  5. Measure supply and ground at the module connector (engine off and cranking/running as needed). Repair wiring if out of tolerance.
  6. Check fuses/relays feeding the module and any dedicated internal regulators. Replace faulty components.
  7. Verify network communication: confirm module is seen on CAN/LIN. If no communication, trace bus to other modules and test termination resistors.
  8. If intermittent communications or CRC errors appear, isolate wiring harness and perform wiggle test while monitoring messages; inspect for shorts to battery or ground.
  9. Check for available software updates or reflash procedure. If recommended by manufacturer, reprogram or perform a controlled reflash per OEM instructions.
  10. If reflash fails or code persists with good power, ground and network, consider module bench testing, repair by specialist, or replacement and correct programming/coding.
  11. After repair or replacement, clear codes, verify communication and functions, and perform a road test to confirm the fault is resolved.

Likely causes

  • Failed internal processor or watchdog timeout
  • Corrupted flash/firmware due to interrupted update
  • Internal supply (5 V or internal regulator) out of tolerance
  • CAN transceiver failure preventing normal communication
  • Damaged connector pins or moisture causing internal short

Fault status

⚠️ Status
Control Module Internal Fault — internal diagnostics detected a hardware or software error (processor, memory, watchdog, regulator, or transceiver). Code may set when the module fails self‑checks or loses ability to communicate or operate reliably; may or may not illuminate a MIL depending on vehicle design.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.0-4.0 hours

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Code

B278A

LEXUS B — Body

Short to GND in Immobiliser System Power Source Circuit

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

Causes

  • Corrupted or failed module software/firmware
  • Internal processor or memory (flash/EEPROM) failure
  • Failed internal power regulator or voltage rail
  • Faulty CAN/LIN transceiver inside the module
  • Intermittent or low supply voltage (battery, fuses, wiring)
  • Water, corrosion, or physical damage to module or connector

Symptoms

  • Malfunction or loss of the functions controlled by the module
  • No communication with the module via scan tool or sporadic responses
  • Illuminated warning lamp(s) or dash messages related to the module
  • Stored B278A and possibly related communication or memory DTCs
  • Intermittent operation or erratic behavior of affected systems

What to check

  • Use a capable scan tool to read B278A plus all stored/freeze‑frame data and related codes
  • Check battery state of charge and battery connections; ensure nominal system voltage (≈12–14 V)
  • Visually inspect module connector, pins and harness for corrosion, bent pins, water intrusion or damage
  • Check relevant fuses, fusible links and power‑distribution relays for continuity
  • Verify module supply and ground voltages at the connector with engine off and cranking
  • Confirm presence and frequency of network messages (CAN/LIN) using scanner or oscilloscope

Signal parameters

  • VBATT at module power pin: ~11–14.5 V (engine off/running as applicable)
  • Ground resistance:
  • Internal 5 V (or module reference rail) if accessible: within manufacturer tolerance
  • CAN bus: expected message IDs for this module present at normal bitrate and periodicity
  • CAN transceiver voltage levels: recessive ~2.5 V, dominant pull low when active
  • Watchdog/reset count: 0 or no frequent unexpected resets (increasing reset count indicates fault)

Diagnostic algorithm

  1. Record DTCs and freeze‑frame data with a professional scan tool. Note any related communication or power DTCs.
  2. Clear codes, then perform a self‑test or key cycles to see if B278A returns immediately or after a specific event.
  3. Verify battery condition and terminal tightness. Repeat with steady nominal battery voltage to rule out low‑voltage corruption.
  4. Inspect connector and harness for contamination, corrosion, bent pins or mechanical damage. Repair or clean as needed.
  5. Measure supply and ground at the module connector (engine off and cranking/running as needed). Repair wiring if out of tolerance.
  6. Check fuses/relays feeding the module and any dedicated internal regulators. Replace faulty components.
  7. Verify network communication: confirm module is seen on CAN/LIN. If no communication, trace bus to other modules and test termination resistors.
  8. If intermittent communications or CRC errors appear, isolate wiring harness and perform wiggle test while monitoring messages; inspect for shorts to battery or ground.
  9. Check for available software updates or reflash procedure. If recommended by manufacturer, reprogram or perform a controlled reflash per OEM instructions.
  10. If reflash fails or code persists with good power, ground and network, consider module bench testing, repair by specialist, or replacement and correct programming/coding.
  11. After repair or replacement, clear codes, verify communication and functions, and perform a road test to confirm the fault is resolved.

Likely causes

  • Failed internal processor or watchdog timeout
  • Corrupted flash/firmware due to interrupted update
  • Internal supply (5 V or internal regulator) out of tolerance
  • CAN transceiver failure preventing normal communication
  • Damaged connector pins or moisture causing internal short

Fault status

⚠️ Status
Control Module Internal Fault — internal diagnostics detected a hardware or software error (processor, memory, watchdog, regulator, or transceiver). Code may set when the module fails self‑checks or loses ability to communicate or operate reliably; may or may not illuminate a MIL depending on vehicle design.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.0-4.0 hours

Similar codes

B2780 B2781 B2782 U0100 U0073 P0606
Repair manuals

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280

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