B2800

Code

HYUNDAI B — Body

MM CAN Bus Off Error

Brand: HYUNDAI

Type: B — Body

Views: UK: 12 EN: 19 RU: 16

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Page language: EN

Multimedia system blank, unresponsive, or intermittent operation
Multiple modules reporting communication errors or loss of functions
CAN-related warning lights/messages on instrument cluster
Other networked devices (e.g., steering wheel controls, phone, navigation) inoperative
DTC B2800 stored and may reappear after clearing
Possible battery drain if a module repeatedly attempts to rejoin bus

Read and record all stored codes on all CAN networks with a capable scan tool
Check for other U-/B-codes that indicate which bus or module is failing
Visually inspect CAN wiring, connectors and grounds for corrosion, damage or water ingress
Measure resistance across CAN_H and CAN_L at vehicle level (expected ~60 Ω with IGN off)
Measure CAN_H and CAN_L voltages with ignition ON and engine OFF using multimeter or scope
Disconnect non-critical nodes (per service manual) one at a time to isolate the fault

Idle recessive voltage: CAN_H ≈ 2.4–2.6 V, CAN_L ≈ 2.4–2.6 V (differential ≈ 0 V)
Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V)
Bus termination: combined resistance ≈ 60 Ω between CAN_H and CAN_L
Typical bus speeds to verify: 125 kb/s, 250 kb/s or 500 kb/s depending on model
Observe waveform for noise, reflections, stuck dominant bits, or repeated error frames

Connect a diagnostic scanner capable of showing bus status and live CAN traffic. Read/record all codes across networks.
Inspect wiring and connectors at the MM module and along the CAN trunk for visible damage, corrosion or water ingress.
With ignition ON (engine OFF), measure CAN_H and CAN_L voltages at the MM connector and at a mid-bus point. Compare to expected signal parameters.
Measure resistance between CAN_H and CAN_L with ignition OFF (expected ~60 Ω). If open or very low, locate short/open.
If short suspected, disconnect connectors progressively (beginning with removable modules per service manual) to isolate the shorted node. Re-measure after each disconnect.
Use an oscilloscope to view waveforms while attempting communication—look for stuck dominant levels, repeated error frames, or reflections.
If an individual module is suspected, swap with a known-good unit (if available) or bench-test the module’s transceiver per OEM procedure.
Repair or replace damaged wiring, connectors, termination resistors, or the defective module. Reconnect and clear codes.
Verify repair by confirming stable CAN traffic, absence of B2800 and related codes, and restoration of affected functions.
If intermittent, perform extended road/test-bench verification to ensure the issue does not recur.

Damaged CAN wiring near the multimedia module or a nearby access point
Failed multimedia (MM) module internal transceiver
One module on the bus stuck dominant (shorted CAN_H to CAN_L or to power/ground)
Missing/failed 120 Ω termination resistor at one or both ends of the bus
Intermittent connector or ground causing repeated error frames and bus-off

⚠️ Status

MM CAN Bus Off — multimedia module detected extended CAN bus errors and entered Bus-Off state; communication to MM lost or unstable.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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B2800 — MM CAN Bus Off Error