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Home / DTC / U0203 — Lost Communication With “Door Control Module E”

U0203 — Lost Communication With “Door Control Module E”

Detailed page for trouble code U0203.

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Code

U0203

HYUNDAI U — Network/User

Lost Communication With “Door Control Module E”

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

Causes

  • Failed Door Control Module E (internal fault)
  • Open, shorted or corroded wiring/connectors between DCM E and CAN/battery/ground
  • Blown fuse or faulty relay supplying the DCM
  • CAN bus short to battery or ground, or open circuit
  • Missing or incorrect bus termination (open/failed resistor)
  • Low battery/voltage supply or intermittent power

Symptoms

  • Door functions not working (central locking, window, mirror, courtesy lights) on affected door(s)
  • Relevant switches/buttons nonfunctional or intermittent
  • Warning or message on instrument cluster indicating door or module fault
  • DTC U0203 stored in BCM/scan tool and DCM E not listed in module list
  • Possible electrical noise or other modules reporting communication errors

What to check

  • Record freeze frame and all stored U-codes with a full OEM-capable scan tool
  • Verify battery voltage (should be ~11–14 V with ignition on) and clean battery terminals
  • Confirm DCM E appears in module list on scan tool; note any other U-codes
  • Check fuses/relays for the DCM and replace if blown
  • Visually inspect connectors and wiring to the affected door (look for corrosion, chaffing, pin damage)
  • Perform wiggle test on harness while monitoring communication with scan tool

Signal parameters

  • Battery/supply to DCM: ~11–14 V with ignition ON
  • CAN_H idle voltage: ~2.5 V (typically rises to ~3.5 V during dominant state)
  • CAN_L idle voltage: ~2.5 V (typically falls to ~1.5 V during dominant state)
  • CAN differential dominant ≈ 2.0 V
  • Termination resistance across CAN_H–CAN_L with power off: ~60 Ω (two 120 Ω in parallel)
  • Data rate: vehicle-specific (commonly 250 kbps or 500 kbps); confirm with OEM docs or scanner

Diagnostic algorithm

  1. Safety: Park vehicle, chock wheels, and disable power if you will be disconnecting modules or connectors.
  2. Read & record codes: Use a capable scan tool to record U0203 and any related codes; note module list and recent events.
  3. Verify battery & fuses: Check battery voltage and inspect/replace fuses supplying DCM E.
  4. Confirm module presence: From scan tool, check if DCM E responds. If absent, continue.
  5. Visual inspection: Inspect connector and wiring to DCM E for damage, corrosion, or water ingress; repair any issues.
  6. Backprobe power/ground: With ignition ON, verify constant/ignition feed and ground at the DCM connector (11–14 V and good ground).
  7. Check CAN bus voltages: Measure CAN_H and CAN_L at the DCM connector with key ON. Compare to expected idle voltages (~2.5 V).
  8. Check termination: With power off, measure resistance across CAN_H–CAN_L (~60 Ω expected).
  9. Isolate the module: Disconnect DCM E and check if the rest of the network communications return; this helps determine if the module is damaging the bus.
  10. Inspect/repair harness: Repair any shorts, opens, or corroded connectors. Restore proper pin-to-pin continuity to the CAN and power circuits.
  11. Reflash/update: If wiring is good and communications restored intermittently, check for software updates or reprogram the module per manufacturer procedures.
  12. Replace module: If DCM E fails diagnostics and communications cannot be restored, replace with a programmed/configured unit per OEM instructions.

Likely causes

  • Damaged or disconnected CAN wiring to DCM E
  • Corroded/loose connector at the door module
  • Blown fuse or lost power to module
  • Failed DCM E module
  • CAN bus short or missing termination resistor

Fault status

⚠️ Status
Lost Communication With "Door Control Module E" — module not responding on CAN/body network
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0200 U0201 U0202 U0204 U0100 U0140
371

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