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Home / DTC / U0050 — Vehicle Communication Bus C (+) High

U0050 — Vehicle Communication Bus C (+) High

Detailed page for trouble code U0050.

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

U0050

Generic U — Network/User

Vehicle Communication Bus C (+) High

Brand: Generic
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short circuit from Bus C (+) to battery voltage (B+)
  • Failed or shorted network transceiver in one or more control modules
  • Damaged wiring or chafed insulation contacting a power source
  • Corroded or loose connector pins on the bus wiring
  • Incorrect or missing termination resistor(s)
  • Water intrusion or contamination in connectors or wiring harness

Symptoms

  • Malfunction indicator lamp (MIL) or communication-related warning lamp illuminated
  • Loss of communication with one or more control modules (modules unavailable)
  • Intermittent or complete failure of subsystems that rely on the bus (ABS, instrument cluster, HVAC, etc.)
  • Erratic gauge/cluster behavior or frozen displays
  • Difficulty starting or no-crank if critical module communications are lost

What to check

  • Scan all modules and record all U-codes and related DTCs
  • Visually inspect wiring harnesses, connectors, and junctions for damage, corrosion, or water intrusion
  • With ignition ON (engine off), measure voltage at the Bus C (+) pin relative to ground using a multimeter
  • Measure resistance between Bus C (+) and battery positive to check for a short to B+
  • Check resistance between Bus C (+) and Bus C (–) — expected ~60 ohms for a properly terminated high-speed CAN (two 120 Ω in parallel)
  • Use a lab oscilloscope with a proper ground reference to observe CANH/CANL waveforms and look for bus stuck/high or noise

Signal parameters

  • Recessive (idle) voltage: CANH ≈ 2.5 V, CANL ≈ 2.5 V (both near mid-rail)
  • Dominant state: CANH ≈ 3.5 V, CANL ≈ 1.5 V (differential ~2.0 V)
  • Expected bus differential: ~2.0 V when dominant, ~0 V when recessive
  • Termination: ~60 Ω measured between CANH and CANL (two 120 Ω terminators in parallel)
  • Fault threshold example: CANH sustained above approximately 5.0 V indicates probable short to battery or driver fault (may vary by manufacturer)

Diagnostic algorithm

  1. Record freeze frame and all stored communication codes. Note affected modules.
  2. Clear codes. Cycle ignition and attempt to reproduce to confirm persistence.
  3. Visually inspect connectors, grounding points, and harness routing for damage or contamination near areas of motion or moisture exposure.
  4. With ignition ON (engine OFF), measure static voltage at the Bus C (+) terminal(s). If voltage is at battery voltage or unusually high, suspect short to B+ or driven high by a transceiver.
  5. Measure resistance from Bus C (+) to battery positive with battery disconnected if possible. A near-short indicates wiring or accessory tied to power.
  6. Measure resistance between Bus C (+) and Bus C (–) to confirm proper termination (~60 Ω). If open or very high resistance, check termination resistors and connector continuity.
  7. Use an oscilloscope to view CANH and CANL waveforms during operation. Look for a bus held high (no differential), excessive spikes, or inconsistent frames.
  8. If bus is driven high, disconnect modules or branches systematically: unplug connectors for suspected modules one at a time while monitoring bus voltage/waveform to identify the module causing the fault.
  9. Inspect and, if necessary, repair or replace damaged wiring, corroded connectors, or the faulty module transceiver. Replace termination resistors if incorrect or damaged.
  10. After repair, clear codes and retest under all operating conditions to ensure the fault does not return.

Likely causes

  • Short to B+ on CANH (Bus C +) at a splice or connector
  • Failed ECU/ECM transceiver driving the bus high
  • Terminal pushed out of connector or corroded pin causing resistance or backfeed
  • Aftermarket device or alarm incorrectly tied into the bus or power rail

Fault status

⚠️ Status
Bus C (+) voltage exceeds allowable range. Communication errors present. Possible short to battery, failed transceiver, damaged wiring/connector, or missing/incorrect termination. Investigate bus voltage, wiring continuity, and module transceivers.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

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Code

U0050

HYUNDAI U — Network/User

Vehicle Communication Bus C (+) High

Brand: HYUNDAI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short circuit from Bus C (+) to battery voltage (B+)
  • Failed or shorted network transceiver in one or more control modules
  • Damaged wiring or chafed insulation contacting a power source
  • Corroded or loose connector pins on the bus wiring
  • Incorrect or missing termination resistor(s)
  • Water intrusion or contamination in connectors or wiring harness

Symptoms

  • Malfunction indicator lamp (MIL) or communication-related warning lamp illuminated
  • Loss of communication with one or more control modules (modules unavailable)
  • Intermittent or complete failure of subsystems that rely on the bus (ABS, instrument cluster, HVAC, etc.)
  • Erratic gauge/cluster behavior or frozen displays
  • Difficulty starting or no-crank if critical module communications are lost

What to check

  • Scan all modules and record all U-codes and related DTCs
  • Visually inspect wiring harnesses, connectors, and junctions for damage, corrosion, or water intrusion
  • With ignition ON (engine off), measure voltage at the Bus C (+) pin relative to ground using a multimeter
  • Measure resistance between Bus C (+) and battery positive to check for a short to B+
  • Check resistance between Bus C (+) and Bus C (–) — expected ~60 ohms for a properly terminated high-speed CAN (two 120 Ω in parallel)
  • Use a lab oscilloscope with a proper ground reference to observe CANH/CANL waveforms and look for bus stuck/high or noise

Signal parameters

  • Recessive (idle) voltage: CANH ≈ 2.5 V, CANL ≈ 2.5 V (both near mid-rail)
  • Dominant state: CANH ≈ 3.5 V, CANL ≈ 1.5 V (differential ~2.0 V)
  • Expected bus differential: ~2.0 V when dominant, ~0 V when recessive
  • Termination: ~60 Ω measured between CANH and CANL (two 120 Ω terminators in parallel)
  • Fault threshold example: CANH sustained above approximately 5.0 V indicates probable short to battery or driver fault (may vary by manufacturer)

Diagnostic algorithm

  1. Record freeze frame and all stored communication codes. Note affected modules.
  2. Clear codes. Cycle ignition and attempt to reproduce to confirm persistence.
  3. Visually inspect connectors, grounding points, and harness routing for damage or contamination near areas of motion or moisture exposure.
  4. With ignition ON (engine OFF), measure static voltage at the Bus C (+) terminal(s). If voltage is at battery voltage or unusually high, suspect short to B+ or driven high by a transceiver.
  5. Measure resistance from Bus C (+) to battery positive with battery disconnected if possible. A near-short indicates wiring or accessory tied to power.
  6. Measure resistance between Bus C (+) and Bus C (–) to confirm proper termination (~60 Ω). If open or very high resistance, check termination resistors and connector continuity.
  7. Use an oscilloscope to view CANH and CANL waveforms during operation. Look for a bus held high (no differential), excessive spikes, or inconsistent frames.
  8. If bus is driven high, disconnect modules or branches systematically: unplug connectors for suspected modules one at a time while monitoring bus voltage/waveform to identify the module causing the fault.
  9. Inspect and, if necessary, repair or replace damaged wiring, corroded connectors, or the faulty module transceiver. Replace termination resistors if incorrect or damaged.
  10. After repair, clear codes and retest under all operating conditions to ensure the fault does not return.

Likely causes

  • Short to B+ on CANH (Bus C +) at a splice or connector
  • Failed ECU/ECM transceiver driving the bus high
  • Terminal pushed out of connector or corroded pin causing resistance or backfeed
  • Aftermarket device or alarm incorrectly tied into the bus or power rail

Fault status

⚠️ Status
Bus C (+) voltage exceeds allowable range. Communication errors present. Possible short to battery, failed transceiver, damaged wiring/connector, or missing/incorrect termination. Investigate bus voltage, wiring continuity, and module transceivers.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

U0051 U0073 U0100 U0101 U0121 U0164
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HYUNDAI

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Code

U0050

MERCEDES-BENZ U — Network/User

Vehicle Communication Bus C (+) high

Brand: MERCEDES-BENZ
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short circuit from Bus C (+) to battery voltage (B+)
  • Failed or shorted network transceiver in one or more control modules
  • Damaged wiring or chafed insulation contacting a power source
  • Corroded or loose connector pins on the bus wiring
  • Incorrect or missing termination resistor(s)
  • Water intrusion or contamination in connectors or wiring harness

Symptoms

  • Malfunction indicator lamp (MIL) or communication-related warning lamp illuminated
  • Loss of communication with one or more control modules (modules unavailable)
  • Intermittent or complete failure of subsystems that rely on the bus (ABS, instrument cluster, HVAC, etc.)
  • Erratic gauge/cluster behavior or frozen displays
  • Difficulty starting or no-crank if critical module communications are lost

What to check

  • Scan all modules and record all U-codes and related DTCs
  • Visually inspect wiring harnesses, connectors, and junctions for damage, corrosion, or water intrusion
  • With ignition ON (engine off), measure voltage at the Bus C (+) pin relative to ground using a multimeter
  • Measure resistance between Bus C (+) and battery positive to check for a short to B+
  • Check resistance between Bus C (+) and Bus C (–) — expected ~60 ohms for a properly terminated high-speed CAN (two 120 Ω in parallel)
  • Use a lab oscilloscope with a proper ground reference to observe CANH/CANL waveforms and look for bus stuck/high or noise

Signal parameters

  • Recessive (idle) voltage: CANH ≈ 2.5 V, CANL ≈ 2.5 V (both near mid-rail)
  • Dominant state: CANH ≈ 3.5 V, CANL ≈ 1.5 V (differential ~2.0 V)
  • Expected bus differential: ~2.0 V when dominant, ~0 V when recessive
  • Termination: ~60 Ω measured between CANH and CANL (two 120 Ω terminators in parallel)
  • Fault threshold example: CANH sustained above approximately 5.0 V indicates probable short to battery or driver fault (may vary by manufacturer)

Diagnostic algorithm

  1. Record freeze frame and all stored communication codes. Note affected modules.
  2. Clear codes. Cycle ignition and attempt to reproduce to confirm persistence.
  3. Visually inspect connectors, grounding points, and harness routing for damage or contamination near areas of motion or moisture exposure.
  4. With ignition ON (engine OFF), measure static voltage at the Bus C (+) terminal(s). If voltage is at battery voltage or unusually high, suspect short to B+ or driven high by a transceiver.
  5. Measure resistance from Bus C (+) to battery positive with battery disconnected if possible. A near-short indicates wiring or accessory tied to power.
  6. Measure resistance between Bus C (+) and Bus C (–) to confirm proper termination (~60 Ω). If open or very high resistance, check termination resistors and connector continuity.
  7. Use an oscilloscope to view CANH and CANL waveforms during operation. Look for a bus held high (no differential), excessive spikes, or inconsistent frames.
  8. If bus is driven high, disconnect modules or branches systematically: unplug connectors for suspected modules one at a time while monitoring bus voltage/waveform to identify the module causing the fault.
  9. Inspect and, if necessary, repair or replace damaged wiring, corroded connectors, or the faulty module transceiver. Replace termination resistors if incorrect or damaged.
  10. After repair, clear codes and retest under all operating conditions to ensure the fault does not return.

Likely causes

  • Short to B+ on CANH (Bus C +) at a splice or connector
  • Failed ECU/ECM transceiver driving the bus high
  • Terminal pushed out of connector or corroded pin causing resistance or backfeed
  • Aftermarket device or alarm incorrectly tied into the bus or power rail

Fault status

⚠️ Status
Bus C (+) voltage exceeds allowable range. Communication errors present. Possible short to battery, failed transceiver, damaged wiring/connector, or missing/incorrect termination. Investigate bus voltage, wiring continuity, and module transceivers.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

U0051 U0073 U0100 U0101 U0121 U0164
856

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

MERCEDES-BENZ

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

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