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Home / DTC / U0010 — Medium Speed CAN Communication Bus

U0010 — Medium Speed CAN Communication Bus

Detailed page for trouble code U0010.

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Code

U0010

MERCEDES-BENZ U — Network/User

Medium Speed CAN Communication Bus

Brand: MERCEDES-BENZ
Type: U — Network/User
AI status
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Page language: EN

Causes

  • Open, short, or damaged CAN wiring or shielding on the medium-speed bus
  • Missing or incorrect termination (open/misaligned 120 Ω terminators or failure of one terminator)
  • Short to battery or ground on CAN_H or CAN_L
  • Faulty or non‑responding module on the medium-speed CAN network
  • Poor ground or power supply to one or more modules on the bus
  • Corroded/loose connectors or damaged pins at module connectors

Symptoms

  • One or more control modules on the medium-speed network show 'no communication' or multiple U-codes
  • Loss or intermittent loss of body, convenience, comfort, or other systems tied to the medium-speed CAN
  • Erratic or incorrect operation of affected modules (doors, windows, mirrors, interior lights, etc.)
  • Multiple unrelated DTCs appearing for modules on the same bus
  • Possible vehicle warning lamps or messages related to communication faults

What to check

  • Use a capable scan tool to read all U-codes and identify which modules are not responding
  • Check vehicle battery voltage and main grounds before network testing
  • Visually inspect wiring harnesses, connectors, and modules for damage, corrosion, or recent service marks
  • Measure resistance between CAN_H and CAN_L (expected ~60 Ω with both terminations present)
  • Measure bus voltages at a module connector with key on - compare CAN_H and CAN_L to expected values
  • Disconnect aftermarket accessories/devices that interface with CAN and re-check bus

Signal parameters

  • Typical medium-speed CAN bit rate commonly 125 kbps (verify vehicle-specific rate before testing)
  • Two-wire differential CAN (typical values): recessive state ~2.5 V on CAN_H and CAN_L; dominant: CAN_H rises toward ~3.5 V and CAN_L falls toward ~1.5 V (differential > ~1.5 V when dominant)
  • Expected termination resistance across CAN_H and CAN_L with connectors attached: approx. 60 Ω (two 120 Ω in parallel)
  • Single-wire/low-speed variants (if present on vehicle): recessive often near vehicle battery voltage, dominant pulled low — consult vehicle service data for exact values
  • Bus must show valid traffic (frames) on a working network when observed with a CAN-capable oscilloscope or scan tool

Diagnostic algorithm

  1. Record all DTCs and freeze-frame data with a scan tool. Note which modules report lost communication.
  2. Verify battery voltage and main chassis/body grounds; correct any low voltage or poor ground conditions.
  3. Inspect medium-speed CAN wiring and connectors visually, focusing on areas of flexing, near doors, hinges, or recent repairs.
  4. With key on, measure DC voltages on CAN_H and CAN_L at a convenient module connector and compare to expected values.
  5. Measure resistance between CAN_H and CAN_L with ignition off to confirm approx. 60 Ω; if open or very low, isolate the segment.
  6. Use a scan tool or CAN scope to observe bus traffic and waveform quality. Identify a module that is not transmitting or a line held dominant.
  7. If bus is shorted, isolate by disconnecting modules one at a time (or sections using connectors/fuses) until normal bus levels/traffic return.
  8. Repair damaged wiring, pins, or connectors; replace faulty modules only after isolating them as the cause. Replace missing/failed termination.
  9. Reprogram or update module software if service information indicates necessary updates after module replacement.
  10. Clear codes and perform a full network check and road/test cycle to confirm repair. Re-scan for reoccurring DTCs.

Likely causes

  • Damaged wiring or connector corrosion in a harness section shared by medium-speed CAN modules
  • Failed module pulling bus dominant (shorting CAN_H to CAN_L or to power/ground)
  • Missing termination resistor(s) or open connection to termination
  • Low battery or poor ground causing intermittent bus communication
  • Recent repairs or aftermarket installations that tapped into the CAN wiring

Fault status

⚠️ Status
Medium Speed CAN Communication Bus — communication fault on the medium-speed CAN network (missing or invalid bus signals).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0001 U0073 U0100 U0121 U0140
856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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