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Home / DTC / U0068 — Vehicle Communication Bus E (+) High

U0068 — Vehicle Communication Bus E (+) High

Detailed page for trouble code U0068.

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Code

U0068

HYUNDAI U — Network/User

Vehicle Communication Bus E (+) High

Brand: HYUNDAI
Type: U — Network/User
Views: UK: 19 EN: 26 RU: 28
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Page language: EN

Causes

  • Short to battery voltage on Bus E (+) wiring or connector
  • Faulty CAN/LIN transceiver in one or more control modules on Bus E
  • Damaged wiring harness (chafing, pinched, corrosion, water ingress)
  • Poor or corroded connector(s) or terminal(s) causing high resistance or intermittent contact
  • Aftermarket equipment or incorrectly wired repairs tapped into the bus
  • Failed module pulling the bus voltage high

Symptoms

  • Multiple warning lights or message center communication errors
  • Loss of function for one or more systems that use Bus E (depends on vehicle configuration)
  • Intermittent or permanent communication warnings on scan tool
  • Possible no-start or limp-home behavior if critical modules are affected
  • Erratic behavior of modules on the affected bus

What to check

  • Read CAN/vehicle network data with a capable scan tool; note modules not responding and related U-codes
  • Visually inspect Bus E wiring, connectors, and junctions for damage, corrosion, or water ingress
  • Check for aftermarket devices or recent repairs on the bus wiring; remove or disable them
  • Measure battery voltage and charging system health to rule out supply issues
  • Perform resistance and continuity checks on Bus E wiring to locate short to B+ or opens
  • Use an oscilloscope to view Bus E + and Bus E - waveforms while the network is active

Signal parameters

  • Expected idle (recessive) CAN High (Bus +) ~2.5 V (varies by network); dominant CAN High ~3.5 V
  • Expected differential CAN voltage: recessive ~0 V differential (both lines ~2.5 V), dominant ~2 V differential
  • If Bus E (+) is being pulled high, measured Bus + will be significantly above expected recessive voltage when idle
  • Look for clean square/fast edges and correct differential waveform on oscilloscope; excessive noise, stuck-high, or clipped waves indicate faults

Diagnostic algorithm

  1. Retrieve freeze frame and full DTC list; record which modules report lost communication and any related U-codes.
  2. Inspect physical wiring, connectors, and junctions for Bus E for damage, corrosion, or recent repairs. Repair any obvious faults.
  3. Disconnect any aftermarket equipment or recently added devices on the bus and re-scan.
  4. With key ON and engine off, measure voltage on Bus E (+) relative to ground at a representative connector. Compare to expected values. If high, isolate sections of the bus by disconnecting connectors/modules one at a time to find the segment causing high voltage.
  5. Use an oscilloscope to inspect Bus E + and Bus E - waveforms while the network is active. Identify nodes causing distorted or stuck-high signals.
  6. If a specific module is suspected, unplug that module and re-check the bus. If the fault clears, investigate or replace the module and inspect its connector/wiring.
  7. Repair wiring or connector faults (splice repair, replace damaged harness, clean/replace terminals) per manufacturer procedures.
  8. Replace faulty control module only after confirming wiring and connector integrity and verifying the module is the source of the fault.
  9. Clear codes, perform a functional test and a drive cycle to confirm the repair. Re-scan for reappearance of U0068 or related codes.

Likely causes

  • Wiring short to B+ on Bus E (+) or connector corrosion
  • Faulty control module transceiver on Bus E
  • Damaged connector or harness at a common junction or splice
  • Aftermarket accessory improperly connected to the network

Fault status

⚠️ Status
Loss or abnormal condition on Vehicle Communication Bus E (+) — voltage higher than expected. Communication with modules on Bus E may be intermittent or lost.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4.0 hours

Similar codes

U0001 U0073 U0077 U0100 U0121
371

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