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Home / DTC / U0013 — Medium speed CAN communication bus (+) low

U0013 — Medium speed CAN communication bus (+) low

Detailed page for trouble code U0013.

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Code

U0013

LAND ROVER U — Network/User

Medium speed CAN communication bus (+) low

Brand: LAND ROVER
Type: U — Network/User
Views: UK: 7 EN: 14 RU: 8
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Page language: EN

Causes

  • Open or short in the CAN+ wiring (to ground or battery)
  • Corroded, damaged or loose connector/pin on CAN+ circuit
  • Failed or intermittent network module driving the CAN+ line
  • Missing or failed termination resistor on the medium‑speed CAN bus
  • Water intrusion or contamination in connectors or harness
  • Aftermarket device or recent repair introduced a wiring fault

Symptoms

  • One or more modules on the medium‑speed CAN network not responding or showing faults
  • Loss of specific vehicle functions controlled over that CAN network (varies by vehicle)
  • Multiple network communication codes present
  • Intermittent or permanent malfunction indicator lamp (MIL) or warning messages
  • Unexpected module behavior after water exposure or connector movement

What to check

  • Retrieve DTCs and freeze frame data with a factory-level scan tool; note time and conditions
  • Check for other U-codes or related module-specific codes to identify affected nodes
  • Visually inspect wiring harnesses, connectors and grommets on known medium‑speed CAN modules for damage, corrosion or water
  • Backprobe CAN+ and CAN- at multiple modules with key ON/engine OFF to compare voltages
  • Measure resistance across CAN+ to CAN- with ignition OFF; expected termination ≈ 60 ohms (two 120Ω in parallel) if two‑wire bus
  • Inspect for aftermarket accessories or recent service that may have disturbed wiring

Signal parameters

  • Typical recessive (idle) voltages (two‑wire CAN): CAN+ ≈ 2.5 V, CAN- ≈ 2.5 V (relative to battery negative)
  • Typical dominant state (two‑wire CAN): CAN+ ≈ 3.5 V, CAN- ≈ 1.5 V; differential ≈ 2.0 V
  • Expected resistance across CAN+ to CAN- with ignition OFF: ≈ 60 ohms (vehicle dependent)
  • Low CAN+ symptom: CAN+ significantly below ~2.0–2.5 V at idle or held low near 0 V

Diagnostic algorithm

  1. Confirm the U0013 code with a scan tool and record related codes and freeze frame.
  2. Visually inspect all medium‑speed CAN connectors and harness routing for damage, corrosion or water ingress; repair or clean as needed.
  3. With ignition ON (engine OFF), backprobe CAN+ and CAN- at a known good module and at the ECU; compare voltages. If CAN+ is low at all nodes, suspect a common short or failed driver.
  4. Measure resistance across CAN+ and CAN- with ignition OFF. If open or far from expected ≈60Ω, locate open or missing termination.
  5. If one module shows a different voltage than others, disconnect that module and recheck the bus to see if the fault clears (module isolation test).
  6. Perform wiggle tests on wiring while monitoring the bus voltage or using an oscilloscope to detect intermittent shorts/opens.
  7. Use a low‑impedance meter or preferably an oscilloscope to inspect waveform integrity for noise, dominant/ recessive transitions and bus errors.
  8. Repair any damaged wiring, correct connector faults, replace faulty terminations, and replace any module confirmed to be driving CAN+ low.
  9. Clear codes and verify repair by rechecking voltages, resistance and performing a road test or use-case test to confirm normal communication.
  10. If intermittent or unresolved, consult wiring diagrams for pinouts, grounding points and module network topology; consider manufacturer technical service bulletins.

Likely causes

  • Connector corrosion or pin pushed out at a module on the medium‑speed CAN ring
  • Short to ground on the CAN+ conductor due to chafing or collapsed insulation
  • Failed module holding CAN+ low or not releasing it
  • Open/shorted termination resistor or incorrect resistance across the bus
  • Damaged harness from previous repairs or routing near moving parts

Fault status

⚠️ Status
Medium speed CAN communication bus positive circuit voltage is lower than expected — indicates an open, short, bad termination or a module fault on the medium‑speed CAN network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours

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U0001 U0073 U0100 U0101 U0140 U0155
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