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Home / DTC / U0032 — Vehicle Communication Bus A (+) High

U0032 — Vehicle Communication Bus A (+) High

Detailed page for trouble code U0032.

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Code

U0032

HYUNDAI U — Network/User

Vehicle Communication Bus A (+) High

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

Causes

  • Open, short or high-resistance fault in CAN H wiring (short to battery or another high-voltage source)
  • Damaged or corroded connector pins at modules or splice points
  • Faulty CAN transceiver inside a control module (ECM, BCM, ABS, etc.)
  • Incorrect or missing termination resistor(s) at bus ends
  • Battery over-voltage or charging system fault
  • Aftermarket electronic device (alarm, radio, tracker) improperly connected to CAN

Symptoms

  • Multiple modules display communication errors or go offline
  • Warning lights on instrument cluster (CAN-related or multiple systems)
  • Intermittent or total loss of functions controlled over CAN (e.g., ABS, climate, infotainment, instrument cluster)
  • Starting issues if PCM/ECM does not communicate
  • Stored U0032 and possibly other U-codes related to lost communication

What to check

  • Read all stored DTCs and freeze-frame with a capable scan tool; note related U-codes
  • Verify battery voltage and charging system health (measure with engine off and running)
  • Visually inspect CAN H and CAN L wiring, connectors and harnesses for damage or corrosion
  • Inspect and secure ground points for affected modules
  • Measure differential and individual line voltages on CAN H and CAN L at a module connector (with key on, engine off)
  • Check termination resistance between CAN H and CAN L with ignition off (~60 ohms typical for two 120Ω terminators in parallel)

Signal parameters

  • Typical CAN recessive state: CAN H ≈ 2.5 V and CAN L ≈ 2.5 V (both lines near mid-supply)
  • Typical CAN dominant state: CAN H rises toward ≈ 3.5 V and CAN L falls toward ≈ 1.5 V
  • With ignition on (no traffic) idle CANH near 2.5 V; sustained CANH significantly above ~3.0–3.3 V indicates a CAN H high condition
  • Termination resistance (ignition off) between CANH and CANL ≈ 60 Ω (two 120 Ω terminators in parallel)

Diagnostic algorithm

  1. Connect a factory-level or bi-directional scan tool, read all U-codes and related module communication errors; record freeze frame.
  2. Check vehicle battery voltage and charging system; correct any over-voltage or low-voltage conditions before network diagnosis.
  3. Visually inspect connectors and wiring for the CAN bus A circuit (follow wiring to ECM, BCM, ABS, gateway/communication module and any splices). Repair visible damage.
  4. With ignition ON (engine OFF), measure CAN H and CAN L voltages at a known good module connector. Compare to expected ranges; note if CAN H is elevated.
  5. With ignition OFF, measure DC resistance between CAN H and CAN L at the same connector; expect ≈ 60 Ω. If open or much lower/higher, investigate terminators and short circuits.
  6. If CAN H reads high, probe for a short to battery: measure resistance from CAN H to B+ with ignition off (should be high/OL). If low resistance to B+, locate damaged wire or module causing short.
  7. Use an oscilloscope to view waveform activity on CAN H and CAN L while the network is active to identify collisions, stuck-high signals, or noise.
  8. Isolate by disconnecting modules one at a time (begin with recently serviced or aftermarket modules) and rechecking the bus after each disconnect to find the offending node.
  9. If a specific module is found to pull CAN H high, replace or repair that module (or its transceiver) and associated connectors/wiring.
  10. After repair, clear codes, confirm normal CAN voltages and good communication to all modules, then road test and re-scan to verify repair.

Likely causes

  • Short to battery/voltage on CAN H circuit
  • Failed module CAN transceiver injecting abnormal voltage
  • Corroded/loose connector or damaged harness at a CAN node
  • Missing/failed termination resistor causing abnormal bus voltages

Fault status

⚠️ Status
U0032 — CAN Bus A (CAN H) voltage above expected threshold detected. Network communication may be interrupted. Inspect CAN H circuit, connectors, termination and modules for short/high-voltage conditions.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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371

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