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Home / DTC / U0005 — High Speed CAN Communication Bus (+) High

U0005 — High Speed CAN Communication Bus (+) High

Detailed page for trouble code U0005.

35,619codes
59brands
11,925generic
23,694specific
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Code

U0005

Generic U — Network/User

High Speed CAN Communication Bus (+) High

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

Causes

  • Short of the CAN High (CAN+) wire to battery voltage (B+) or another high-voltage source
  • Damaged or chafed wiring harness causing a short or intermittent contact
  • Corroded, loose or damaged connector pins on CAN bus nodes
  • Failed CAN transceiver (inside a control module) pulling CAN High high
  • Incorrect or missing termination resistor(s) on the CAN bus
  • Aftermarket device or repair wiring incorrectly connected to the CAN bus

Symptoms

  • Multiple modules showing communication errors or going offline
  • Intermittent or permanent loss of instrument cluster, engine ECU, or ABS messages
  • Illuminated MIL or multiple warning lamps
  • Erratic instrument cluster gauges or displays
  • Starter/crankability or no-start if critical module communications are lost
  • Unable to communicate with modules using a scan tool or modules appear as 'not responding'

What to check

  • Make sure vehicle battery is at normal voltage and fully charged before testing
  • Visual inspection of CAN High and CAN Low wiring, harness clamps, and connectors for damage or corrosion
  • Backprobe the CAN High and CAN Low at an accessible connector and measure voltages with key on, engine off
  • Measure resistance between CAN High and battery positive with key removed (looking for low resistance short)
  • Measure resistance between CAN High and CAN Low (expected ~60 ohm total with both terminations present)
  • Check presence and condition of termination resistors (typically 120 ohm across CAN_H and CAN_L or two 60 ohm in parallel)

Signal parameters

  • Recessive level (idle) CAN_H ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Recessive level CAN_L ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Dominant level CAN_H ≈ 3.3–3.9 V, CAN_L ≈ 0.9–1.5 V (differential ≈2.0 V)
  • Expected DC difference between CAN_H and battery (B+) should be several volts lower than B+; CAN_H tied to B+ indicates fault
  • Expected bus differential idle ≈ 0 V to small offset; dominant pulses ≈ 2 V differential
  • Total bus termination resistance typically ≈ 60 ohm (two 120 ohm in parallel) measured across CAN_H and CAN_L with power off

Diagnostic algorithm

  1. Safety: Disable vehicle and take electrostatic precautions. Record stored codes and freeze frame data.
  2. Inspect visually for obvious wiring damage, melted insulation, or water intrusion at connectors and module housings.
  3. With key ON (engine off), measure DC voltage on CAN_H and CAN_L relative to ground at a convenient connector. Note values and compare to expected ranges.
  4. If CAN_H is significantly higher than expected (near battery voltage), remove power to suspected circuits and measure resistance from CAN_H to B+ to confirm a short.
  5. Check termination: with battery disconnected, measure resistance across CAN_H and CAN_L. Approximately 60 ohms indicates proper termination; open/very high or very low values indicate missing/shorted termination.
  6. Use an oscilloscope to observe CAN waveforms while operating the network (start key sequence, wiggle connectors). Look for DC offset, stuck high, no transitions, or excessive noise.
  7. Isolate the fault by disconnecting modules or sub-harnesses one at a time (start with modules added or near recent repairs). If fault clears when a module is disconnected, suspect that module or its harness.
  8. Inspect and service any aftermarket devices or recently replaced modules/wiring tied into the CAN bus.
  9. If a module transceiver is suspected, verify its supply and ground circuits. Replace only after confirming the transceiver is faulty and not caused by wiring.
  10. Repair damaged wiring or connector pins. Replace termination resistors or modules as required. Clear codes and road-test; verify the code does not return.

Likely causes

  • Short to B+ on CAN High wiring (most common for a 'High' signal)
  • Failed module transceiver driving CAN High high
  • Damaged connector pin or water intrusion at a gateway/module
  • Missing or damaged 120 ohm termination or parallel termination fault

Fault status

⚠️ Status
CAN High line voltage above expected range. Network communication errors detected. Investigate CAN_H short to voltage, wiring/connectors, termination, or failed transceiver.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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Code

U0005

HYUNDAI U — Network/User

High Speed CAN Communication Bus (+) High

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

Causes

  • Short of the CAN High (CAN+) wire to battery voltage (B+) or another high-voltage source
  • Damaged or chafed wiring harness causing a short or intermittent contact
  • Corroded, loose or damaged connector pins on CAN bus nodes
  • Failed CAN transceiver (inside a control module) pulling CAN High high
  • Incorrect or missing termination resistor(s) on the CAN bus
  • Aftermarket device or repair wiring incorrectly connected to the CAN bus

Symptoms

  • Multiple modules showing communication errors or going offline
  • Intermittent or permanent loss of instrument cluster, engine ECU, or ABS messages
  • Illuminated MIL or multiple warning lamps
  • Erratic instrument cluster gauges or displays
  • Starter/crankability or no-start if critical module communications are lost
  • Unable to communicate with modules using a scan tool or modules appear as 'not responding'

What to check

  • Make sure vehicle battery is at normal voltage and fully charged before testing
  • Visual inspection of CAN High and CAN Low wiring, harness clamps, and connectors for damage or corrosion
  • Backprobe the CAN High and CAN Low at an accessible connector and measure voltages with key on, engine off
  • Measure resistance between CAN High and battery positive with key removed (looking for low resistance short)
  • Measure resistance between CAN High and CAN Low (expected ~60 ohm total with both terminations present)
  • Check presence and condition of termination resistors (typically 120 ohm across CAN_H and CAN_L or two 60 ohm in parallel)

Signal parameters

  • Recessive level (idle) CAN_H ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Recessive level CAN_L ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Dominant level CAN_H ≈ 3.3–3.9 V, CAN_L ≈ 0.9–1.5 V (differential ≈2.0 V)
  • Expected DC difference between CAN_H and battery (B+) should be several volts lower than B+; CAN_H tied to B+ indicates fault
  • Expected bus differential idle ≈ 0 V to small offset; dominant pulses ≈ 2 V differential
  • Total bus termination resistance typically ≈ 60 ohm (two 120 ohm in parallel) measured across CAN_H and CAN_L with power off

Diagnostic algorithm

  1. Safety: Disable vehicle and take electrostatic precautions. Record stored codes and freeze frame data.
  2. Inspect visually for obvious wiring damage, melted insulation, or water intrusion at connectors and module housings.
  3. With key ON (engine off), measure DC voltage on CAN_H and CAN_L relative to ground at a convenient connector. Note values and compare to expected ranges.
  4. If CAN_H is significantly higher than expected (near battery voltage), remove power to suspected circuits and measure resistance from CAN_H to B+ to confirm a short.
  5. Check termination: with battery disconnected, measure resistance across CAN_H and CAN_L. Approximately 60 ohms indicates proper termination; open/very high or very low values indicate missing/shorted termination.
  6. Use an oscilloscope to observe CAN waveforms while operating the network (start key sequence, wiggle connectors). Look for DC offset, stuck high, no transitions, or excessive noise.
  7. Isolate the fault by disconnecting modules or sub-harnesses one at a time (start with modules added or near recent repairs). If fault clears when a module is disconnected, suspect that module or its harness.
  8. Inspect and service any aftermarket devices or recently replaced modules/wiring tied into the CAN bus.
  9. If a module transceiver is suspected, verify its supply and ground circuits. Replace only after confirming the transceiver is faulty and not caused by wiring.
  10. Repair damaged wiring or connector pins. Replace termination resistors or modules as required. Clear codes and road-test; verify the code does not return.

Likely causes

  • Short to B+ on CAN High wiring (most common for a 'High' signal)
  • Failed module transceiver driving CAN High high
  • Damaged connector pin or water intrusion at a gateway/module
  • Missing or damaged 120 ohm termination or parallel termination fault

Fault status

⚠️ Status
CAN High line voltage above expected range. Network communication errors detected. Investigate CAN_H short to voltage, wiring/connectors, termination, or failed transceiver.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0001 U0073 U0077 U0100 U0121 U0140
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

U0005

LAND ROVER U — Network/User

High-speed CAN communication bus (+) high

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

Causes

  • Short of the CAN High (CAN+) wire to battery voltage (B+) or another high-voltage source
  • Damaged or chafed wiring harness causing a short or intermittent contact
  • Corroded, loose or damaged connector pins on CAN bus nodes
  • Failed CAN transceiver (inside a control module) pulling CAN High high
  • Incorrect or missing termination resistor(s) on the CAN bus
  • Aftermarket device or repair wiring incorrectly connected to the CAN bus

Symptoms

  • Multiple modules showing communication errors or going offline
  • Intermittent or permanent loss of instrument cluster, engine ECU, or ABS messages
  • Illuminated MIL or multiple warning lamps
  • Erratic instrument cluster gauges or displays
  • Starter/crankability or no-start if critical module communications are lost
  • Unable to communicate with modules using a scan tool or modules appear as 'not responding'

What to check

  • Make sure vehicle battery is at normal voltage and fully charged before testing
  • Visual inspection of CAN High and CAN Low wiring, harness clamps, and connectors for damage or corrosion
  • Backprobe the CAN High and CAN Low at an accessible connector and measure voltages with key on, engine off
  • Measure resistance between CAN High and battery positive with key removed (looking for low resistance short)
  • Measure resistance between CAN High and CAN Low (expected ~60 ohm total with both terminations present)
  • Check presence and condition of termination resistors (typically 120 ohm across CAN_H and CAN_L or two 60 ohm in parallel)

Signal parameters

  • Recessive level (idle) CAN_H ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Recessive level CAN_L ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Dominant level CAN_H ≈ 3.3–3.9 V, CAN_L ≈ 0.9–1.5 V (differential ≈2.0 V)
  • Expected DC difference between CAN_H and battery (B+) should be several volts lower than B+; CAN_H tied to B+ indicates fault
  • Expected bus differential idle ≈ 0 V to small offset; dominant pulses ≈ 2 V differential
  • Total bus termination resistance typically ≈ 60 ohm (two 120 ohm in parallel) measured across CAN_H and CAN_L with power off

Diagnostic algorithm

  1. Safety: Disable vehicle and take electrostatic precautions. Record stored codes and freeze frame data.
  2. Inspect visually for obvious wiring damage, melted insulation, or water intrusion at connectors and module housings.
  3. With key ON (engine off), measure DC voltage on CAN_H and CAN_L relative to ground at a convenient connector. Note values and compare to expected ranges.
  4. If CAN_H is significantly higher than expected (near battery voltage), remove power to suspected circuits and measure resistance from CAN_H to B+ to confirm a short.
  5. Check termination: with battery disconnected, measure resistance across CAN_H and CAN_L. Approximately 60 ohms indicates proper termination; open/very high or very low values indicate missing/shorted termination.
  6. Use an oscilloscope to observe CAN waveforms while operating the network (start key sequence, wiggle connectors). Look for DC offset, stuck high, no transitions, or excessive noise.
  7. Isolate the fault by disconnecting modules or sub-harnesses one at a time (start with modules added or near recent repairs). If fault clears when a module is disconnected, suspect that module or its harness.
  8. Inspect and service any aftermarket devices or recently replaced modules/wiring tied into the CAN bus.
  9. If a module transceiver is suspected, verify its supply and ground circuits. Replace only after confirming the transceiver is faulty and not caused by wiring.
  10. Repair damaged wiring or connector pins. Replace termination resistors or modules as required. Clear codes and road-test; verify the code does not return.

Likely causes

  • Short to B+ on CAN High wiring (most common for a 'High' signal)
  • Failed module transceiver driving CAN High high
  • Damaged connector pin or water intrusion at a gateway/module
  • Missing or damaged 120 ohm termination or parallel termination fault

Fault status

⚠️ Status
CAN High line voltage above expected range. Network communication errors detected. Investigate CAN_H short to voltage, wiring/connectors, termination, or failed transceiver.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0001 U0073 U0077 U0100 U0121 U0140
413

Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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Code

U0005

MERCEDES-BENZ U — Network/User

High Speed CAN Communication Bus (+) high

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

Causes

  • Short of the CAN High (CAN+) wire to battery voltage (B+) or another high-voltage source
  • Damaged or chafed wiring harness causing a short or intermittent contact
  • Corroded, loose or damaged connector pins on CAN bus nodes
  • Failed CAN transceiver (inside a control module) pulling CAN High high
  • Incorrect or missing termination resistor(s) on the CAN bus
  • Aftermarket device or repair wiring incorrectly connected to the CAN bus

Symptoms

  • Multiple modules showing communication errors or going offline
  • Intermittent or permanent loss of instrument cluster, engine ECU, or ABS messages
  • Illuminated MIL or multiple warning lamps
  • Erratic instrument cluster gauges or displays
  • Starter/crankability or no-start if critical module communications are lost
  • Unable to communicate with modules using a scan tool or modules appear as 'not responding'

What to check

  • Make sure vehicle battery is at normal voltage and fully charged before testing
  • Visual inspection of CAN High and CAN Low wiring, harness clamps, and connectors for damage or corrosion
  • Backprobe the CAN High and CAN Low at an accessible connector and measure voltages with key on, engine off
  • Measure resistance between CAN High and battery positive with key removed (looking for low resistance short)
  • Measure resistance between CAN High and CAN Low (expected ~60 ohm total with both terminations present)
  • Check presence and condition of termination resistors (typically 120 ohm across CAN_H and CAN_L or two 60 ohm in parallel)

Signal parameters

  • Recessive level (idle) CAN_H ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Recessive level CAN_L ≈ 2.5 V (typical range ~2.0–3.0 V)
  • Dominant level CAN_H ≈ 3.3–3.9 V, CAN_L ≈ 0.9–1.5 V (differential ≈2.0 V)
  • Expected DC difference between CAN_H and battery (B+) should be several volts lower than B+; CAN_H tied to B+ indicates fault
  • Expected bus differential idle ≈ 0 V to small offset; dominant pulses ≈ 2 V differential
  • Total bus termination resistance typically ≈ 60 ohm (two 120 ohm in parallel) measured across CAN_H and CAN_L with power off

Diagnostic algorithm

  1. Safety: Disable vehicle and take electrostatic precautions. Record stored codes and freeze frame data.
  2. Inspect visually for obvious wiring damage, melted insulation, or water intrusion at connectors and module housings.
  3. With key ON (engine off), measure DC voltage on CAN_H and CAN_L relative to ground at a convenient connector. Note values and compare to expected ranges.
  4. If CAN_H is significantly higher than expected (near battery voltage), remove power to suspected circuits and measure resistance from CAN_H to B+ to confirm a short.
  5. Check termination: with battery disconnected, measure resistance across CAN_H and CAN_L. Approximately 60 ohms indicates proper termination; open/very high or very low values indicate missing/shorted termination.
  6. Use an oscilloscope to observe CAN waveforms while operating the network (start key sequence, wiggle connectors). Look for DC offset, stuck high, no transitions, or excessive noise.
  7. Isolate the fault by disconnecting modules or sub-harnesses one at a time (start with modules added or near recent repairs). If fault clears when a module is disconnected, suspect that module or its harness.
  8. Inspect and service any aftermarket devices or recently replaced modules/wiring tied into the CAN bus.
  9. If a module transceiver is suspected, verify its supply and ground circuits. Replace only after confirming the transceiver is faulty and not caused by wiring.
  10. Repair damaged wiring or connector pins. Replace termination resistors or modules as required. Clear codes and road-test; verify the code does not return.

Likely causes

  • Short to B+ on CAN High wiring (most common for a 'High' signal)
  • Failed module transceiver driving CAN High high
  • Damaged connector pin or water intrusion at a gateway/module
  • Missing or damaged 120 ohm termination or parallel termination fault

Fault status

⚠️ Status
CAN High line voltage above expected range. Network communication errors detected. Investigate CAN_H short to voltage, wiring/connectors, termination, or failed transceiver.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0001 U0073 U0077 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.

MERCEDES-BENZ

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

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