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Home / DTC / C1404 — CAN Bus Off

C1404 — CAN Bus Off

Detailed page for trouble code C1404.

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C1404

HYUNDAI C — Chassis

CAN Bus Off

Brand: HYUNDAI
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to battery or ground on CAN_H or CAN_L
  • Open or high-resistance wiring/connections in CAN circuit
  • Failed control module driving the bus dominant
  • Missing or incorrect bus termination (open/shorted 120Ω terminator(s))
  • Low vehicle battery/poor main ground or intermittent power
  • Water ingress/corrosion at connectors or junctions

Symptoms

  • Multiple control modules not responding to scan tool
  • Illuminated warning lamps (ABS, ESC, engine, instrument cluster failures)
  • Intermittent or complete loss of vehicle network functions
  • Starter/communication-related no-crank or limp modes in some vehicles
  • Intermittent faults that reset after reconnecting battery or modules

What to check

  • Connect a capable scan tool and confirm CAN Bus Off condition and related U/C codes
  • Check battery voltage (with key off and during cranking) and main ground integrity
  • Visually inspect CAN wiring, connectors, junction blocks and modules for damage or corrosion
  • Measure resistance between CAN_H and CAN_L with ignition OFF (expect ~60Ω across the two terminators)
  • Measure CAN_H and CAN_L voltages with key ON and engine OFF using a DVM or preferably a scope
  • Disconnect suspected modules one at a time to see if bus returns to normal (isolate offending module)

Signal parameters

  • CAN_H idle voltage: approx. 2.5 V to 3.5 V (single‑ended)
  • CAN_L idle voltage: approx. 1.5 V to 2.5 V (single‑ended)
  • Recessive differential voltage: approx. 0 V to small mV (lines roughly equal)
  • Dominant differential voltage: approx. 1.5 V to 2.5 V (CAN_H higher than CAN_L)
  • Termination resistance: approx. 60 Ω measured across CAN_H and CAN_L (two 120 Ω termini in parallel)

Diagnostic algorithm

  1. Read all stored DTCs and freeze frame with scan tool; record related U and C codes.
  2. Check battery state of charge and main ground connections; restore proper battery voltage if low.
  3. Visually inspect CAN harness, T‑junctions, splice points and module connectors for damage, corrosion or water.
  4. With ignition OFF, measure continuity and resistance between CAN_H and CAN_L at a convenient connector — expect ~60 Ω. If open or very low, trace wiring.
  5. With key ON, measure CAN_H and CAN_L voltages to battery negative. Abnormal single‑ended voltages indicate short to Vb or ground.
  6. Use an oscilloscope to view waveforms on both lines while exercising systems. Look for a line stuck dominant (flat low/high) or heavy noise.
  7. If unable to identify from measurements, disconnect suspect modules one at a time (starting with recent service area or where waveform shows issue) and re-check bus status after each disconnect to isolate the offending module or branch.
  8. Repair or replace damaged wiring, connectors, or faulty module identified. Replace missing/incorrect termination resistors if necessary.
  9. After repairs, clear codes, perform relearns if required, and road test while monitoring CAN traffic to confirm restoration.
  10. If fault persists after harness and connector repair, consider module bench testing or replacement following OEM procedures.

Likely causes

  • Damaged/shorted CAN wiring near a connector or splice
  • Faulty module holding CAN lines dominant (module internal failure)
  • Loss of termination resistor (open/short) or multiple terminations
  • Bad battery/ground causing network instability

Fault status

⚠️ Status
CAN Bus Off — one or more modules have lost CAN network communication or the bus is held in a dominant/off state; communication with some modules may be lost.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0073 U0100 U0140 U0155 C1201
371

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